drm/amdgpu: indirect register access for nv12 sriov

unify host driver and guest driver indirect access
control bits names

Signed-off-by: Peng Ju Zhou <PengJu.Zhou@amd.com>
Reviewed-by: Emily.Deng <Emily.Deng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>