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/meth.c b/drivers/net/meth.c
index 9f72cb4..16a3594 100644
--- a/drivers/net/meth.c
+++ b/drivers/net/meth.c
@@ -746,7 +746,7 @@
 	/* Enable interrupt */
 	spin_unlock_irqrestore(&priv->meth_lock, flags);
 
-	dev->trans_start = jiffies;
+	dev->trans_start = jiffies; /* prevent tx timeout */
 	netif_wake_queue(dev);
 
 	return;