net: Convert nfnl_log_net_ops

These pernet_operations create and destroy /proc entries.
Also, exit method unsets nfulnl_logger. The logger is not
set by default, and it becomes bound via userspace request.
So, they look safe to be made async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/nfnetlink_log.c

@@ -1108,6 +1108,7 @@ static struct pernet_operations nfnl_log_net_ops = {
 	.exit	= nfnl_log_net_exit,
 	.id	= &nfnl_log_net_id,
 	.size	= sizeof(struct nfnl_log_net),
+	.async	= true,
 };
 
 static int __init nfnetlink_log_init(void)