net: Convert cfg80211_pernet_ops

This patch finishes converting pernet_operations
registered in net/wireless directory.

These pernet_operations have only exit method,
which moves devices to init_net. This action
is not pernet_operations-specific, and function
cfg80211_switch_netns() may be called all time
during the system life. All necessary protection
against concurrent cfg80211_pernet_exit() is made
by rtnl_lock(). So, cfg80211_pernet_ops is able
to be marked as async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/wireless/core.c

@@ -1340,6 +1340,7 @@ static void __net_exit cfg80211_pernet_exit(struct net *net)
 
 static struct pernet_operations cfg80211_pernet_ops = {
 	.exit = cfg80211_pernet_exit,
+	.async = true,
 };
 
 static int __init cfg80211_init(void)