drm/amdgpu: enable pptable ucode loading

With SCPM enabled, pptable cannot be uploaded to SMU directly.
The transferring has to be via PSP.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>