rt2x00: Fix queue->qid initialization

As Adam Baker reported the queue->qid was not initialized
correctly. The QID_AC_BE was assigned to the RX ring.

This will move the queue initialization into a seperate function
and makes sure that all queues are initialized directly with the
correct qids.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>