KVM: VMX: Ignore MKTME KeyID bits when intercepting #PF for allow_smaller_maxphyaddr

KVM: VMX: Ignore MKTME KeyID bits when intercepting #PF for allow_smaller_maxphyaddr

Use the raw/true host.MAXPHYADDR when deciding whether or not KVM must
intercept #PFs when allow_smaller_maxphyaddr is enabled, as any adjustments
the kernel makes to boot_cpu_data.x86_phys_bits to account for MKTME KeyID
bits do not apply to the guest physical address space.  I.e. the KeyID are
off-limits for host physical addresses, but are not reserved for GPAs as
far as hardware is concerned.

Signed-off-by: Tao Su <tao1.su@linux.intel.com>
Link: https://lore.kernel.org/r/20240319031111.495006-1-tao1.su@linux.intel.com
[sean: massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>