net: Convert ip6mr_net_ops

These pernet_operations create and destroy /proc entries,
populate and depopulate net::rules_ops and multiroute table.
All the structures are pernet, and they are not touched
by foreign net pernet_operations. So, it's possible to mark
them async.
Signed-off-by: NKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/ip6mr.c

@@ -1397,6 +1397,7 @@ static void __net_exit ip6mr_net_exit(struct net *net)
 static struct pernet_operations ip6mr_net_ops = {
 	.init = ip6mr_net_init,
 	.exit = ip6mr_net_exit,
+	.async = true,
 };
 
 int __init ip6_mr_init(void)