net: Convert iptable_filter_net_ops

These pernet_operations register and unregister
net::ipv4.iptable_filter table. Since there are
no packets in-flight at the time of exit method
is working, iptables rules should not be touched.
Also, pernet_operations should not send ipv4
packets each other. So, it's safe to mark them
async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/iptable_filter.c

@@ -87,6 +87,7 @@ static void __net_exit iptable_filter_net_exit(struct net *net)
 static struct pernet_operations iptable_filter_net_ops = {
 	.init = iptable_filter_net_init,
 	.exit = iptable_filter_net_exit,
+	.async = true,
 };
 
 static int __init iptable_filter_init(void)