netdev: change name dropping error codes

If changename notifier returns an error code, it gets incorrectly
cleared during rollback so the error is never returned to the user.
Found while testing similar code for MTU changes.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index 868ec0b..b8a4fd0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -924,10 +924,10 @@
 		strlcpy(dev->name, newname, IFNAMSIZ);
 
 rollback:
-	err = device_rename(&dev->dev, dev->name);
-	if (err) {
+	ret = device_rename(&dev->dev, dev->name);
+	if (ret) {
 		memcpy(dev->name, oldname, IFNAMSIZ);
-		return err;
+		return ret;
 	}
 
 	write_lock_bh(&dev_base_lock);