drm/amdgpu: add psp block load condition for sienna_cichlid

Enable PSP block for firmware loading and other security
setup only when amdgpu use PSP load type to load ucode.

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>