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/sungem.c b/drivers/net/sungem.c
index 2b78e97..5bc786f 100644
--- a/drivers/net/sungem.c
+++ b/drivers/net/sungem.c
@@ -1136,7 +1136,7 @@
 	writel(gp->tx_new, gp->regs + TXDMA_KICK);
 	spin_unlock_irqrestore(&gp->tx_lock, flags);
 
-	dev->trans_start = jiffies;
+	dev->trans_start = jiffies; /* NETIF_F_LLTX driver :( */
 
 	return NETDEV_TX_OK;
 }