net/xen-netfront: add kernel TX timestamps

This adds kernel TX timestamps to the xen-netfront driver.  Tested with chrony
on an AWS EC2 instance.
Signed-off-by: Daniel Drown <dan-netdev@drown.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/xen-netfront.c

@@ -754,6 +754,9 @@ static netdev_tx_t xennet_start_xmit(struct sk_buff *skb, struct net_device *dev
 	/* First request has the packet length. */
 	first_tx->size = skb->len;
 
+	/* timestamp packet in software */
+	skb_tx_timestamp(skb);
+
 	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&queue->tx, notify);
 	if (notify)
 		notify_remote_via_irq(queue->tx_irq);
@@ -2411,6 +2414,7 @@ static const struct ethtool_ops xennet_ethtool_ops =
 	.get_sset_count = xennet_get_sset_count,
 	.get_ethtool_stats = xennet_get_ethtool_stats,
 	.get_strings = xennet_get_strings,
+	.get_ts_info = ethtool_op_get_ts_info,
 };
 
 #ifdef CONFIG_SYSFS