drm/amdgpu: skip fw pri bo alloc for SRIOV

PSP fw primary buffer is not used under SRIOV.
Under SRIOV, VBIOS or hypervisor driver will load psp
sos and psp sysdrv. Therefore, we don't need to
allocate memory for it.

v2: remove superfluous check for amdgpu_bo_free_kernel().

Signed-off-by: Yintian Tao <yttao@amd.com>
Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>