r8169: enable transmit time stamping.

This patch has been tested on a machine with the Realtek
RTL8101E/RTL8102E PCI Express Fast Ethernet controller (rev 05).

Cc: Realtek linux nic maintainers <nic_swsd@realtek.com>
Cc: Francois Romieu <romieu@fr.zoreil.com>

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index 4aa4194..27c358c 100644
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -5154,6 +5154,8 @@
 
 	netdev_sent_queue(dev, skb->len);
 
+	skb_tx_timestamp(skb);
+
 	wmb();
 
 	/* Anti gcc 2.95.3 bugware (sic) */