net: ena: Relocate skb_tx_timestamp() to improve time stamping accuracy

Move skb_tx_timestamp() closer to the actual time the driver sends the
packets to the device.
Signed-off-by: Osama Abboud <osamaabb@amazon.com>
Signed-off-by: David Arinzon <darinzon@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/amazon/ena/ena_netdev.c

@@ -2614,8 +2614,6 @@ static netdev_tx_t ena_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (unlikely(rc))
 		goto error_drop_packet;
 
-	skb_tx_timestamp(skb);
-
 	next_to_use = tx_ring->next_to_use;
 	req_id = tx_ring->free_ids[next_to_use];
 	tx_info = &tx_ring->tx_buffer_info[req_id];
@@ -2679,6 +2677,8 @@ static netdev_tx_t ena_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		}
 	}
 
+	skb_tx_timestamp(skb);
+
 	if (netif_xmit_stopped(txq) || !netdev_xmit_more())
 		/* trigger the dma engine. ena_ring_tx_doorbell()
 		 * calls a memory barrier inside it.