net: remove empty netlink_tap_exit_net

Pointer members of an object with static storage duration, if not
explicitly initialized, will be initialized to a NULL pointer. The
net namespace API checks if this pointer is not NULL before using it,
it are safe to remove the function.
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/af_netlink.c

@@ -241,13 +241,8 @@ static __net_init int netlink_tap_init_net(struct net *net)
 	return 0;
 }
 
-static void __net_exit netlink_tap_exit_net(struct net *net)
-{
-}
-
 static struct pernet_operations netlink_tap_net_ops = {
 	.init = netlink_tap_init_net,
-	.exit = netlink_tap_exit_net,
 	.id   = &netlink_tap_net_id,
 	.size = sizeof(struct netlink_tap_net),
 };