[PATCH -next] tile: fix missing unlock on error in tile_net_open()

From: Wei Yongjun <redacted>

Add the missing unlock before return from function tile_net_open()
in the error handling case.

Introduced by commit f3286a3af89d6db7a488f3e8f02b98d67d50f00c.
(tile: support multiple mPIPE shims in tilegx network driver)

Signed-off-by: Wei Yongjun <redacted>
---
 drivers/net/ethernet/tile/tilegx.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/tile/tilegx.c b/drivers/net/ethernet/tile/tilegx.c
index 907b577..5d2a719 100644
--- a/drivers/net/ethernet/tile/tilegx.c
+++ b/drivers/net/ethernet/tile/tilegx.c

@@ -1510,8 +1510,10 @@ static int tile_net_open(struct net_device *dev)
 
 	/* Get the instance info. */
 	rc = gxio_mpipe_link_instance(dev->name);
-	if (rc < 0 || rc >= NR_MPIPE_MAX)
+	if (rc < 0 || rc >= NR_MPIPE_MAX) {
+		mutex_unlock(&tile_net_devs_for_channel_mutex);
 		return -EIO;
+	}
 
 	priv->instance = rc;
 	instance = rc;