[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>

drivers/isdn/i4l/isdn_tty.c

@@ -1223,7 +1223,7 @@ isdn_tty_write(struct tty_struct *tty, const u_char * buf, int count)
 		total += c;
 	}
 	atomic_dec(&info->xmit_lock);
-	if ((info->xmit_count) || (skb_queue_len(&info->xmit_queue))) {
+	if ((info->xmit_count) || !skb_queue_empty(&info->xmit_queue)) {
 		if (m->mdmreg[REG_DXMT] & BIT_DXMT) {
 			isdn_tty_senddown(info);
 			isdn_tty_tint(info);
@@ -1284,7 +1284,7 @@ isdn_tty_flush_chars(struct tty_struct *tty)
 
 	if (isdn_tty_paranoia_check(info, tty->name, "isdn_tty_flush_chars"))
 		return;
-	if ((info->xmit_count) || (skb_queue_len(&info->xmit_queue)))
+	if ((info->xmit_count) || !skb_queue_empty(&info->xmit_queue))
 		isdn_timer_ctrl(ISDN_TIMER_MODEMXMIT, 1);
 }