drm/mediatek: Support 180 degree rotation

Now that we support both reflections, we can expose 180 degree rotation
and rely on the simplify routine to convert that into REFLECT_X |
REFLECT_Y

Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: CK Hu <ck.hu@mediatek.com>

drivers/gpu/drm/mediatek/mtk_disp_ovl.c

@@ -143,8 +143,8 @@ static unsigned int mtk_ovl_layer_nr(struct mtk_ddp_comp *comp)
 
 static unsigned int mtk_ovl_supported_rotations(struct mtk_ddp_comp *comp)
 {
-	return DRM_MODE_ROTATE_0 | DRM_MODE_REFLECT_Y |
-	       DRM_MODE_REFLECT_X;
+	return DRM_MODE_ROTATE_0 | DRM_MODE_ROTATE_180 |
+	       DRM_MODE_REFLECT_X | DRM_MODE_REFLECT_Y;
 }
 
 static int mtk_ovl_layer_check(struct mtk_ddp_comp *comp, unsigned int idx,