drm/amdgpu: refine virtualization psp fw skip check

SR-IOV may need to load different firmwares for different ASIC inside
VF.
So create a new function in amdgpu_virt to check whether FW load needs
to be skipped.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Horace Chen <horace.chen@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>