drm/amdkfd: fix null pointer panic while free buffer in kfd

drm/amdkfd: fix null pointer panic while free buffer in kfd

In drm_gem_object_free, it will call funcs of drm buffer obj. So
kfd_alloc should use amdgpu_gem_object_create instead of
amdgpu_bo_create to initialize the funcs as amdgpu_gem_object_funcs.

[  396.231390] amdgpu: Release VA 0x7f76b4ada000 - 0x7f76b4add000
[  396.231394] amdgpu:   remove VA 0x7f76b4ada000 - 0x7f76b4add000 in entry 0000000085c24a47
[  396.231408] BUG: kernel NULL pointer dereference, address: 0000000000000000
[  396.231445] #PF: supervisor read access in kernel mode
[  396.231466] #PF: error_code(0x0000) - not-present page
[  396.231484] PGD 0 P4D 0
[  396.231495] Oops: 0000 [#1] SMP NOPTI
[  396.231509] CPU: 7 PID: 1352 Comm: clinfo Tainted: G           OE     5.11.0-rc2-custom #1
[  396.231537] Hardware name: AMD Celadon-RN/Celadon-RN, BIOS WCD0401N_Weekly_20_04_0 04/01/2020
[  396.231563] RIP: 0010:drm_gem_object_free+0xc/0x22 [drm]
[  396.231606] Code: eb ec 48 89 c3 eb e7 0f 1f 44 00 00 55 48 89 e5 48 8b bf 00 06 00 00 e8 72 0d 01 00 5d c3 0f 1f 44 00 00 48 8b 87 40 01 00 00 <48> 8b 00 48 85 c0 74 0b 55 48 89 e5 e8 54 37 7c db 5d c3 0f 0b c3
[  396.231666] RSP: 0018:ffffb4704177fcf8 EFLAGS: 00010246
[  396.231686] RAX: 0000000000000000 RBX: ffff993a0d0cc400 RCX: 0000000000003113
[  396.231711] RDX: 0000000000000001 RSI: e9cda7a5d0791c6d RDI: ffff993a333a9058
[  396.231736] RBP: ffffb4704177fdd0 R08: ffff993a03855858 R09: 0000000000000000
[  396.231761] R10: ffff993a0d1f7158 R11: 0000000000000001 R12: 0000000000000000
[  396.231785] R13: ffff993a0d0cc428 R14: 0000000000003000 R15: ffffb4704177fde0
[  396.231811] FS:  00007f76b5730740(0000) GS:ffff993b275c0000(0000) knlGS:0000000000000000
[  396.231840] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  396.231860] CR2: 0000000000000000 CR3: 000000016d2e2000 CR4: 0000000000350ee0
[  396.231885] Call Trace:
[  396.231897]  ? amdgpu_amdkfd_gpuvm_free_memory_of_gpu+0x24c/0x25f [amdgpu]
[  396.232056]  ? __dynamic_dev_dbg+0xcd/0x100
[  396.232076]  kfd_ioctl_free_memory_of_gpu+0x91/0x102 [amdgpu]
[  396.232214]  kfd_ioctl+0x211/0x35b [amdgpu]
[  396.232341]  ? kfd_ioctl_get_queue_wave_state+0x52/0x52 [amdgpu]

Fixes: 246cb7e49a70 ("drm/amdgpu: Introduce GEM object functions")
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Tested-by: Changfeng <changzhu@amd.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org