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/slip.c b/drivers/net/slip.c
index 8969615..d92772e 100644
--- a/drivers/net/slip.c
+++ b/drivers/net/slip.c
@@ -458,7 +458,7 @@
 		 *      14 Oct 1994 Dmitry Gorodchanin.
 		 */
 #ifdef SL_CHECK_TRANSMIT
-		if (time_before(jiffies, dev->trans_start + 20 * HZ))  {
+		if (time_before(jiffies, dev_trans_start(dev) + 20 * HZ))  {
 			/* 20 sec timeout not reached */
 			goto out;
 		}