net: trans_start cleanups

Now that core network takes care of trans_start updates, dont do it
in drivers themselves, if possible. Drivers can avoid one cache miss
(on dev->trans_start) in their start_xmit() handler.

Exceptions are NETIF_F_LLTX drivers

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ewrk3.c b/drivers/net/ewrk3.c
index 11ba70f..99eb56b 100644
--- a/drivers/net/ewrk3.c
+++ b/drivers/net/ewrk3.c
@@ -757,7 +757,7 @@
 		 */
 		ENABLE_IRQs;
 
-		dev->trans_start = jiffies;
+		dev->trans_start = jiffies; /* prevent tx timeout */
 		netif_wake_queue(dev);
 	}
 }
@@ -862,7 +862,6 @@
 	spin_unlock_irq (&lp->hw_lock);
 
 	dev->stats.tx_bytes += skb->len;
-	dev->trans_start = jiffies;
 	dev_kfree_skb (skb);
 
 	/* Check for free resources: stop Tx queue if there are none */