drm/amdgpu: add helper to query rlcg reg access flag

Query rlc indirect register access approach specified
by sriov host driver per ip blocks

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Zhou, Peng Ju <PengJu.Zhou@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>