ath9k: limit tx path hang check to normal data queues

The beacon and multicast-buffer queues are managed by the beacon
tasklet, and the generic tx path hang check does not help in any way
here. Running it on those queues anyway can introduce some race
conditions leading to unnecessary chip resets.

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