ath9k: fix block ack window tracking check

When a packet has been tracked as part of the BlockAck window and added
to the hardware queue, it can end up back in the TID queue again with
fi->retries still set to 0 (e.g. if the frame was filtered). Keep an
extra bit for the BAW tracking status to fix this corner case.

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