drm/amdgpu: enable rom clock gating for rn

Enable rom light sleep clock gating.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/soc15.c

@@ -1167,7 +1167,8 @@ static int soc15_common_early_init(void *handle)
 				 AMD_CG_SUPPORT_SDMA_MGCG |
 				 AMD_CG_SUPPORT_SDMA_LS |
 				 AMD_CG_SUPPORT_BIF_LS |
-				 AMD_CG_SUPPORT_HDP_LS;
+				 AMD_CG_SUPPORT_HDP_LS |
+				 AMD_CG_SUPPORT_ROM_MGCG;
 		adev->pg_flags = 0;
 		adev->external_rev_id = adev->rev_id + 0x91;