net: Convert inet6_net_ops

init method initializes sysctl defaults, allocates
percpu arrays and creates /proc entries.
exit method reverts the above.

There are no pernet_operations, which are interested
in the above entities of foreign net namespace, so
inet6_net_ops are able to be marked as async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/af_inet6.c

@@ -857,6 +857,7 @@ static void __net_exit inet6_net_exit(struct net *net)
 static struct pernet_operations inet6_net_ops = {
 	.init = inet6_net_init,
 	.exit = inet6_net_exit,
+	.async = true,
 };
 
 static const struct ipv6_stub ipv6_stub_impl = {