AA: ath9k: remove most of the tx queueing rework until it has been fully debugged

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@37920 3c298f89-4303-0410-b956-a3cf2f4a3e73