drm/amdgpu: enable gfx clock gatings for navi12

enables following gfx clock gating features:

- medium grained clock gating
- medium grained light sleep
- coarse grained clock gating
- cp memory light sleep
- rlc memory light sleep

CGLS (Coarse Grained Light Sleep) will break s3, so don't enable it.
Signed-off-by: Xiaojie Yuan <xiaojie.yuan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/nv.c

@@ -641,7 +641,11 @@ static int nv_common_early_init(void *handle)
 		adev->external_rev_id = adev->rev_id + 20;
 		break;
 	case CHIP_NAVI12:
-		adev->cg_flags = 0;
+		adev->cg_flags = AMD_CG_SUPPORT_GFX_MGCG |
+			AMD_CG_SUPPORT_GFX_MGLS |
+			AMD_CG_SUPPORT_GFX_CGCG |
+			AMD_CG_SUPPORT_GFX_CP_LS |
+			AMD_CG_SUPPORT_GFX_RLC_LS;
 		adev->pg_flags = AMD_PG_SUPPORT_VCN_DPG;
 		adev->external_rev_id = adev->rev_id + 0xa;
 		break;