net: Convert ip6_flowlabel_net_ops

These pernet_operations create and destroy /proc entries.
ip6_fl_purge() makes almost the same actions as timer
ip6_fl_gc_timer does, and as it can be executed in parallel
with ip6_fl_purge(), two parallel ip6_fl_purge() may be
executed. So, we can mark it async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_flowlabel.c

@@ -873,6 +873,7 @@ static void __net_exit ip6_flowlabel_net_exit(struct net *net)
 static struct pernet_operations ip6_flowlabel_net_ops = {
 	.init = ip6_flowlabel_proc_init,
 	.exit = ip6_flowlabel_net_exit,
+	.async = true,
 };
 
 int ip6_flowlabel_init(void)