netdevice: add netdev_tx_reset_subqueue() shorthand

Add a shorthand similar to other net*_subqueue() helpers for resetting
the queue by its index w/o obtaining &netdev_tx_queue beforehand
manually.

Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>