[NET]: Transform skb_queue_len() binary tests into skb_queue_empty()

This is part of the grand scheme to eliminate the qlen
member of skb_queue_head, and subsequently remove the
'list' member of sk_buff.

Most users of skb_queue_len() want to know if the queue is
empty or not, and that's trivially done with skb_queue_empty()
which doesn't use the skb_queue_head->qlen member and instead
uses the queue list emptyness as the test.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_red.c b/net/sched/sch_red.c
index 664d0e4..7845d04 100644
--- a/net/sched/sch_red.c
+++ b/net/sched/sch_red.c
@@ -385,7 +385,7 @@
 	memcpy(q->Stab, RTA_DATA(tb[TCA_RED_STAB-1]), 256);
 
 	q->qcount = -1;
-	if (skb_queue_len(&sch->q) == 0)
+	if (skb_queue_empty(&sch->q))
 		PSCHED_SET_PASTPERFECT(q->qidlestart);
 	sch_tree_unlock(sch);
 	return 0;