net: add missing dev_put() in __netdev_adjacent_dev_insert

I think that a dev_put() is needed in the error path to preserve the
proper dev refcount.

CC: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Acked-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -4648,6 +4648,7 @@ static int __netdev_adjacent_dev_insert(struct net_device *dev,
 
 free_adj:
 	kfree(adj);
+	dev_put(adj_dev);
 
 	return ret;
 }