ath9k: Remove redundant data structure ath9k_txq_info

Use ath9k_tx_queue_info which contains the same elements,
and merge get/set functions of tx queue properties.
Also, fix whitespace damage in struct ath_softc.

Signed-off-by: Sujith Manoharan <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>