e100: enable transmit time stamping.

This patch enables software (and phy device) transmit time stamping.
Tested on an old PIII laptop with built in NIC.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/e100.c

@@ -1759,6 +1759,7 @@ static void e100_xmit_prepare(struct nic *nic, struct cb *cb,
 		skb->data, skb->len, PCI_DMA_TODEVICE));
 	/* check for mapping failure? */
 	cb->u.tcb.tbd.size = cpu_to_le16(skb->len);
+	skb_tx_timestamp(skb);
 }
 
 static netdev_tx_t e100_xmit_frame(struct sk_buff *skb,