Revert "ath9k_hw: Fix false tx hung detection in AR9003 chips"

The approach of this change is flawed, as it triggers tx status processing
from more callsites, yet the chips only have one global tx status queue.
Subsequent patches will properly fix the issue that this one tried to address.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>