e1000e: Do not allow requeue of freed skb

Returning BUSY will make qdisc_restart enqueue the skb which was already
freed. The bad skb was correctly freed and we should return NETDEV_TX_OK.

First spotted by Jeff Garzik on 08/13/07.
Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/e1000e/netdev.c

@@ -3531,7 +3531,7 @@ static int e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 		/* handle pci_map_single() error in e1000_tx_map */
 		dev_kfree_skb_any(skb);
 		spin_unlock_irqrestore(&adapter->tx_queue_lock, irq_flags);
-		return NETDEV_TX_BUSY;
+		return NETDEV_TX_OK;
 	}
 
 	e1000_tx_queue(adapter, tx_flags, count);