synclink_gt fix locking in error path of rx enable

Fix locking in error path of rx_enable() introduced by
synclink_gt-add-rx-dma-buffer-fill-level-control patch.

Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/synclink_gt.c

@@ -2686,8 +2686,10 @@ static int rx_enable(struct slgt_info *info, int enable)
 	 */
 	rbuf_fill_level = ((unsigned int)enable) >> 16;
 	if (rbuf_fill_level) {
-		if ((rbuf_fill_level > DMABUFSIZE) || (rbuf_fill_level % 4))
+		if ((rbuf_fill_level > DMABUFSIZE) || (rbuf_fill_level % 4)) {
+			spin_unlock_irqrestore(&info->lock, flags);
 			return -EINVAL;
+		}
 		info->rbuf_fill_level = rbuf_fill_level;
 		rx_stop(info); /* restart receiver to use new fill level */
 	}