[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/decnet/dn_nsp_out.c b/net/decnet/dn_nsp_out.c
index 42abbf3..8cce1fd 100644
--- a/net/decnet/dn_nsp_out.c
+++ b/net/decnet/dn_nsp_out.c
@@ -342,7 +342,8 @@
 
 	dn_nsp_output(sk);
 
-	if (skb_queue_len(&scp->data_xmit_queue) || skb_queue_len(&scp->other_xmit_queue))
+	if (!skb_queue_empty(&scp->data_xmit_queue) ||
+	    !skb_queue_empty(&scp->other_xmit_queue))
 		scp->persist = dn_nsp_persist(sk);
 
 	return 0;