net: Convert ip_vs_ftp_ops

These pernet_operations register and unregister ipvs app.
register_ip_vs_app(), unregister_ip_vs_app() and
register_ip_vs_app_inc() modify per-net structures,
and there are no global structures touched. So,
this looks safe to be marked as async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/ipvs/ip_vs_ftp.c

@@ -479,6 +479,7 @@ static void __ip_vs_ftp_exit(struct net *net)
 static struct pernet_operations ip_vs_ftp_ops = {
 	.init = __ip_vs_ftp_init,
 	.exit = __ip_vs_ftp_exit,
+	.async = true,
 };
 
 static int __init ip_vs_ftp_init(void)