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/wireless/prism54/islpci_eth.c

@@ -224,8 +224,6 @@ islpci_eth_transmit(struct sk_buff *skb, struct net_device *ndev)
 		priv->data_low_tx_full = 1;
 	}
 
-	/* set the transmission time */
-	ndev->trans_start = jiffies;
 	ndev->stats.tx_packets++;
 	ndev->stats.tx_bytes += skb->len;