smsc911x: enable transmit time stamping.

This patch enables software (and phy device) transmit time stamping.
Compile tested only.

Cc: Steve Glendinning <steve.glendinning@smsc.com>
Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/smsc911x.c

@@ -1474,6 +1474,7 @@ static int smsc911x_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	pdata->ops->tx_writefifo(pdata, (unsigned int *)bufp, wrsz);
 	freespace -= (skb->len + 32);
+	skb_tx_timestamp(skb);
 	dev_kfree_skb(skb);
 
 	if (unlikely(smsc911x_tx_get_txstatcount(pdata) >= 30))