net: sched: cls: use nla_nest_cancel instead of nlmsg_trim

To cancel nesting, this function is more convenient.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c
index 741bfa7..221697a 100644
--- a/net/sched/cls_cgroup.c
+++ b/net/sched/cls_cgroup.c
@@ -177,7 +177,6 @@
 			   struct sk_buff *skb, struct tcmsg *t)
 {
 	struct cls_cgroup_head *head = rtnl_dereference(tp->root);
-	unsigned char *b = skb_tail_pointer(skb);
 	struct nlattr *nest;
 
 	t->tcm_handle = head->handle;
@@ -198,7 +197,7 @@
 	return skb->len;
 
 nla_put_failure:
-	nlmsg_trim(skb, b);
+	nla_nest_cancel(skb, nest);
 	return -1;
 }