ath9k_hw: fix hardware queue allocation

The driver passes the desired hardware queue index for a WMM data queue
in qinfo->tqi_subtype. This was ignored in ath9k_hw_setuptxqueue, which
instead relied on the order in which the function is called.

Cc: stable@vger.kernel.org
Reported-by: Hubert Feurstein <h.feurstein@gmail.com>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>