net: txq_trans_update() helper

We would like to get rid of netdev->trans_start = jiffies; that about all net
drivers have to use in their start_xmit() function, and use txq->trans_start
instead.

This can be done generically in core network, as suggested by David.

Some devices, (particularly loopback) dont need trans_start update, because
they dont have transmit watchdog. We could add a new device flag, or rely
on fact that txq->tran_start can be updated is txq->xmit_lock_owner is
different than -1. Use a helper function to hide our choice.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_teql.c b/net/sched/sch_teql.c
index 428a5ef..a886496 100644
--- a/net/sched/sch_teql.c
+++ b/net/sched/sch_teql.c
@@ -308,6 +308,7 @@
 				if (!netif_tx_queue_stopped(slave_txq) &&
 				    !netif_tx_queue_frozen(slave_txq) &&
 				    slave_ops->ndo_start_xmit(skb, slave) == 0) {
+					txq_trans_update(slave_txq);
 					__netif_tx_unlock(slave_txq);
 					master->slaves = NEXT_SLAVE(q);
 					netif_wake_queue(dev);