net_sched: sch_netem: use rb_entry()

To make the code clearer, use rb_entry() instead of container_of() to
deal with rbtree.
Signed-off-by: NGeliang Tang <geliangtang@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/sch_netem.c

@@ -152,7 +152,7 @@ struct netem_skb_cb {
 
 static struct sk_buff *netem_rb_to_skb(struct rb_node *rb)
 {
-	return container_of(rb, struct sk_buff, rbnode);
+	return rb_entry(rb, struct sk_buff, rbnode);
 }
 
 static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)