net: Fix ks8851 snl NULL pointer dereference Oops

This fixes the NULL pointer dereference Oops in the ks8851 snl network
driver during transmission.  All socket buffers from the queue are
processed inside the loop, but new workqueues have been scheduled to
run.
Signed-off-by: NTristram Ha <Tristram.Ha@micrel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ks8851.c

-/* drivers/net/ks8651.c
+/* drivers/net/ks8851.c
  *
  * Copyright 2009 Simtec Electronics
  *	http://www.simtec.co.uk/
@@ -714,7 +714,7 @@ static void ks8851_tx_work(struct work_struct *work)
 {
 	struct ks8851_net *ks = container_of(work, struct ks8851_net, tx_work);
 	struct sk_buff *txb;
-	bool last = false;
+	bool last = skb_queue_empty(&ks->txq);
 
 	mutex_lock(&ks->lock);