rockchip: video: Flush the cache when the display is updated

Enable this option to correct display artifacts when a write-back cache is
in use.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/video/rockchip/rk_vop.c

@@ -326,6 +326,7 @@ static int rk_vop_probe(struct udevice *dev)
 		if (!ret)
 			break;
 	}
+	video_set_flush_dcache(dev, 1);
 
 	return ret;
 }