net: Convert ip_tables_net_ops, udplite6_net_ops and xt_net_ops

ip_tables_net_ops and udplite6_net_ops create and destroy /proc entries.
xt_net_ops does nothing.

So, we are able to mark them async.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 2f685ee..a6a435d 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -1765,6 +1765,7 @@ static void __net_exit xt_net_exit(struct net *net)
 static struct pernet_operations xt_net_ops = {
 	.init = xt_net_init,
 	.exit = xt_net_exit,
+	.async = true,
 };
 
 static int __init xt_init(void)