drm/amdgpu: disable gfxoff for sienna_cichlid

Temporary disable gfxoff for sienna_cichlid.
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>

drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c

@@ -3531,6 +3531,9 @@ static void gfx_v10_0_check_gfxoff_flag(struct amdgpu_device *adev)
 		if (!gfx_v10_0_navi10_gfxoff_should_enable(adev))
 			adev->pm.pp_feature &= ~PP_GFXOFF_MASK;
 		break;
+	case CHIP_SIENNA_CICHLID:
+		adev->pm.pp_feature &= ~PP_GFXOFF_MASK;
+		break;
 	default:
 		break;
 	}