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/sb1250-mac.c b/drivers/net/sb1250-mac.c
index fec3c29..1f3acc3 100644
--- a/drivers/net/sb1250-mac.c
+++ b/drivers/net/sb1250-mac.c
@@ -2068,8 +2068,6 @@
 		return NETDEV_TX_BUSY;
 	}
 
-	dev->trans_start = jiffies;
-
 	spin_unlock_irqrestore(&sc->sbm_lock, flags);
 
 	return NETDEV_TX_OK;
@@ -2488,7 +2486,7 @@
 	spin_lock_irqsave(&sc->sbm_lock, flags);
 
 
-	dev->trans_start = jiffies;
+	dev->trans_start = jiffies; /* prevent tx timeout */
 	dev->stats.tx_errors++;
 
 	spin_unlock_irqrestore(&sc->sbm_lock, flags);