net: core: add __netdev_sent_queue as variant of __netdev_tx_sent_queue

Similar to netdev_sent_queue add helper __netdev_sent_queue as variant
of __netdev_tx_sent_queue.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>