drm/amdgpu:add PSP block only load_type=PSP (v2)

SRIOV currently only can load ucode directly, and PSP
block is not supported by VF temporarily.

will remove this restrict and use PSP load all ucode
even for SRIOV later

v2: squash in check against module parameter

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