net: Convert nfnetlink_net_ops

These pernet_operations create and destroy net::nfnl
socket of NETLINK_NETFILTER code. There are no other
places, where such type the socket is created, except
these pernet_operations. It seem other pernet_operations
depending on CONFIG_NETFILTER_NETLINK send messages
to this socket. So, we mark it async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/nfnetlink.c

@@ -566,6 +566,7 @@ static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 static struct pernet_operations nfnetlink_net_ops = {
 	.init		= nfnetlink_net_init,
 	.exit_batch	= nfnetlink_net_exit_batch,
+	.async		= true,
 };
 
 static int __init nfnetlink_init(void)