net: ethernet: ti: netcp_core: remove netif_trans_update

No need to update jiffies in txq->trans_start twice and only for tx 0,
it's supposed to be done in netdev_start_xmit() and per tx queue.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>