video: Allow syncing the entire framebuffer to the copy

In some cases so much of the framebuffer is updated that it is not worth
copying the changes piece by piece to the copy framebuffer. Add a function
to copy the whole thing.

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

drivers/video/video-uclass.c

@@ -290,6 +290,16 @@ int video_sync_copy(struct udevice *dev, void *from, void *to)
 
 	return 0;
 }
+
+int video_sync_copy_all(struct udevice *dev)
+{
+	struct video_priv *priv = dev_get_uclass_priv(dev);
+
+	video_sync_copy(dev, priv->fb, priv->fb + priv->fb_size);
+
+	return 0;
+}
+
 #endif
 
 /* Set up the colour map */