[NETNS]: init dev_base_lock only once

* it already statically initialized
* reinitializing live global spinlock every time netns is
  setup is also wrong
Signed-off-by: NAlexey Dobriyan <adobriyan@sw.ru>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -4330,7 +4330,6 @@ static struct hlist_head *netdev_create_hash(void)
 static int __net_init netdev_init(struct net *net)
 {
 	INIT_LIST_HEAD(&net->dev_base_head);
-	rwlock_init(&dev_base_lock);
 
 	net->dev_name_head = netdev_create_hash();
 	if (net->dev_name_head == NULL)