drm/amdgpu: fix null pointer deref in firmware header printing

drm/amdgpu: fix null pointer deref in firmware header printing

v2: declare as (struct common_firmware_header *) type because
    struct xxx_firmware_header inherits from it

When CE's ucode_id(8) is used to get sdma_hdr, we will be accessing an
unallocated amdgpu_firmware_info instance.

This issue appears on rhel7.7 with gcc 4.8.5. Newer compilers might have
optimized out such 'defined but not referenced' variable.

[ 1120.798564] BUG: unable to handle kernel NULL pointer dereference at 000000000000000a
[ 1120.806703] IP: [<ffffffffc0e3c9b3>] psp_np_fw_load+0x1e3/0x390 [amdgpu]
[ 1120.813693] PGD 80000002603ff067 PUD 271b8d067 PMD 0
[ 1120.818931] Oops: 0000 [#1] SMP
[ 1120.822245] Modules linked in: amdgpu(OE+) amdkcl(OE) amd_iommu_v2 amdttm(OE) amd_sched(OE) xt_CHECKSUM ipt_MASQUERADE nf_nat_masquerade_ipv4 tun bridge stp llc devlink ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 xt_conntrack ebtable_nat ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat iptable_mangle iptable_security iptable_raw nf_conntrack libcrc32c ip_set nfnetlink ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter sunrpc dm_mirror dm_region_hash dm_log dm_mod intel_pmc_core intel_powerclamp coretemp intel_rapl joydev kvm_intel eeepc_wmi asus_wmi kvm sparse_keymap iTCO_wdt irqbypass rfkill crc32_pclmul snd_hda_codec_realtek mxm_wmi ghash_clmulni_intel intel_wmi_thunderbolt iTCO_vendor_support snd_hda_codec_generic snd_hda_codec_hdmi aesni_intel lrw gf128mul glue_helper ablk_helper sg cryptd pcspkr snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer snd pinctrl_sunrisepoint pinctrl_intel soundcore acpi_pad mei_me wmi mei i2c_i801 pcc_cpufreq ip_tables ext4 mbcache jbd2 sd_mod crc_t10dif crct10dif_generic i915 i2c_algo_bit iosf_mbi drm_kms_helper e1000e syscopyarea sysfillrect sysimgblt fb_sys_fops ahci libahci drm ptp libata crct10dif_pclmul crct10dif_common crc32c_intel serio_raw pps_core drm_panel_orientation_quirks video i2c_hid
[ 1120.954136] CPU: 4 PID: 2426 Comm: modprobe Tainted: G           OE  ------------   3.10.0-1062.el7.x86_64 #1
[ 1120.964390] Hardware name: System manufacturer System Product Name/Z170-A, BIOS 1302 11/09/2015
[ 1120.973321] task: ffff991ef1e3c1c0 ti: ffff991ee625c000 task.ti: ffff991ee625c000
[ 1120.981020] RIP: 0010:[<ffffffffc0e3c9b3>]  [<ffffffffc0e3c9b3>] psp_np_fw_load+0x1e3/0x390 [amdgpu]
[ 1120.990483] RSP: 0018:ffff991ee625f950  EFLAGS: 00010202
[ 1120.995935] RAX: 0000000000000002 RBX: ffff991edf6b2d38 RCX: ffff991edf6a0000
[ 1121.003391] RDX: 0000000000000000 RSI: ffff991f01d13898 RDI: ffffffffc110afb3
[ 1121.010706] RBP: ffff991ee625f9b0 R08: 0000000000000000 R09: 0000000000000000
[ 1121.018029] R10: 00000000000004c4 R11: ffff991ee625f64e R12: ffff991edf6b3220
[ 1121.025353] R13: ffff991edf6a0000 R14: 0000000000000008 R15: ffff991edf6b2d30
[ 1121.032666] FS:  00007f97b0c0b740(0000) GS:ffff991f01d00000(0000) knlGS:0000000000000000
[ 1121.041000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1121.046880] CR2: 000000000000000a CR3: 000000025e604000 CR4: 00000000003607e0
[ 1121.054239] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 1121.061631] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 1121.068938] Call Trace:
[ 1121.071494]  [<ffffffffc0e3dba8>] psp_hw_init+0x218/0x270 [amdgpu]
[ 1121.077886]  [<ffffffffc0da3188>] amdgpu_device_fw_loading+0xe8/0x160 [amdgpu]
[ 1121.085296]  [<ffffffffc0e3b34c>] ? vega10_ih_irq_init+0x4bc/0x730 [amdgpu]
[ 1121.092534]  [<ffffffffc0da5c75>] amdgpu_device_init+0x1495/0x1c90 [amdgpu]
[ 1121.099675]  [<ffffffffc0da9cab>] amdgpu_driver_load_kms+0x8b/0x2f0 [amdgpu]
[ 1121.106888]  [<ffffffffc01b25cf>] drm_dev_register+0x12f/0x1d0 [drm]
[ 1121.113419]  [<ffffffffa4dcdfd8>] ? pci_enable_device_flags+0xe8/0x140
[ 1121.120183]  [<ffffffffc0da260a>] amdgpu_pci_probe+0xca/0x170 [amdgpu]
[ 1121.126919]  [<ffffffffa4dcf97a>] local_pci_probe+0x4a/0xb0
[ 1121.132622]  [<ffffffffa4dd10c9>] pci_device_probe+0x109/0x160
[ 1121.138607]  [<ffffffffa4eb4205>] driver_probe_device+0xc5/0x3e0
[ 1121.144766]  [<ffffffffa4eb4603>] __driver_attach+0x93/0xa0
[ 1121.150507]  [<ffffffffa4eb4570>] ? __device_attach+0x50/0x50
[ 1121.156422]  [<ffffffffa4eb1da5>] bus_for_each_dev+0x75/0xc0
[ 1121.162213]  [<ffffffffa4eb3b7e>] driver_attach+0x1e/0x20
[ 1121.167771]  [<ffffffffa4eb3620>] bus_add_driver+0x200/0x2d0
[ 1121.173590]  [<ffffffffa4eb4c94>] driver_register+0x64/0xf0
[ 1121.179345]  [<ffffffffa4dd0905>] __pci_register_driver+0xa5/0xc0
[ 1121.185593]  [<ffffffffc099f000>] ? 0xffffffffc099efff
[ 1121.190914]  [<ffffffffc099f0a4>] amdgpu_init+0xa4/0xb0 [amdgpu]
[ 1121.197101]  [<ffffffffa4a0210a>] do_one_initcall+0xba/0x240
[ 1121.202901]  [<ffffffffa4b1c90a>] load_module+0x271a/0x2bb0
[ 1121.208598]  [<ffffffffa4dad740>] ? ddebug_proc_write+0x100/0x100
[ 1121.214894]  [<ffffffffa4b1ce8f>] SyS_init_module+0xef/0x140
[ 1121.220698]  [<ffffffffa518bede>] system_call_fastpath+0x25/0x2a
[ 1121.226870] Code: b4 01 60 a2 00 00 31 c0 e8 83 60 33 e4 41 8b 47 08 48 8b 4d d0 48 c7 c7 b3 af 10 c1 48 69 c0 68 07 00 00 48 8b 84 01 60 a2 00 00 <48> 8b 70 08 31 c0 48 89 75 c8 e8 56 60 33 e4 48 8b 4d d0 48 c7
[ 1121.247422] RIP  [<ffffffffc0e3c9b3>] psp_np_fw_load+0x1e3/0x390 [amdgpu]
[ 1121.254432]  RSP <ffff991ee625f950>
[ 1121.258017] CR2: 000000000000000a
[ 1121.261427] ---[ end trace e98b35387ede75bd ]---

Signed-off-by: Xiaojie Yuan <xiaojie.yuan@amd.com>
Fixes: c5fb912653dae3f878 ("drm/amdgpu: add firmware header printing for psp fw loading (v2)")
Reviewed-by: Kevin Wang <kevin1.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>