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>

drivers/net/irda/pxaficp_ir.c

@@ -556,7 +556,6 @@ static int pxa_irda_hard_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	dev_kfree_skb(skb);
-	dev->trans_start = jiffies;
 	return NETDEV_TX_OK;
 }