net: Convert arp_tables_net_ops and ip6_tables_net_ops

These pernet_operations call xt_proto_init() and xt_proto_fini(),
which just register and unregister /proc entries.
They are safe to be marked as async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/arp_tables.c

@@ -1635,6 +1635,7 @@ static void __net_exit arp_tables_net_exit(struct net *net)
 static struct pernet_operations arp_tables_net_ops = {
 	.init = arp_tables_net_init,
 	.exit = arp_tables_net_exit,
+	.async = true,
 };
 
 static int __init arp_tables_init(void)

net/ipv6/netfilter/ip6_tables.c

@@ -1928,6 +1928,7 @@ static void __net_exit ip6_tables_net_exit(struct net *net)
 static struct pernet_operations ip6_tables_net_ops = {
 	.init = ip6_tables_net_init,
 	.exit = ip6_tables_net_exit,
+	.async = true,
 };
 
 static int __init ip6_tables_init(void)