6LoWPAN: call dev_put() on error in lowpan_newlink()

We should release the dev_hold() on error before returning here.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ieee802154/6lowpan.c

@@ -793,8 +793,11 @@ static int lowpan_newlink(struct net *src_net, struct net_device *dev,
 	mutex_init(&lowpan_dev_info(dev)->dev_list_mtx);
 
 	entry = kzalloc(sizeof(struct lowpan_dev_record), GFP_KERNEL);
-	if (!entry)
+	if (!entry) {
+		dev_put(real_dev);
+		lowpan_dev_info(dev)->real_dev = NULL;
 		return -ENOMEM;
+	}
 
 	entry->ldev = dev;