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/at1700.c b/drivers/net/at1700.c
index 332f980..861f07a 100644
--- a/drivers/net/at1700.c
+++ b/drivers/net/at1700.c
@@ -583,7 +583,7 @@
 	outb (0x00, ioaddr + TX_START);
 	outb (0x03, ioaddr + COL16CNTL);
 
-	dev->trans_start = jiffies;
+	dev->trans_start = jiffies; /* prevent tx timeout */
 
 	lp->tx_started = 0;
 	lp->tx_queue_ready = 1;
@@ -636,7 +636,6 @@
 		outb (0x80 | lp->tx_queue, ioaddr + TX_START);
 		lp->tx_queue = 0;
 		lp->tx_queue_len = 0;
-		dev->trans_start = jiffies;
 		lp->tx_started = 1;
 		netif_start_queue (dev);
 	} else if (lp->tx_queue_len < 4096 - 1502)