ar9170: simplify & deBUG tx_status queueing and reporting

This patch simplifies the tx_status report code by using four tx_queues per
station instead of only one. (the skb lookup should be in O(1) now :-p ).

Also, it fixes a really obvious copy&paste bug in the janitor work code and
adds back a few spilled bits to the hardware definition header about QoS.

Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>