ath9k: fix tx aggregation flush on AR9003

ath9k: fix tx aggregation flush on AR9003

commit e609e2ea2cdb3448e7849703179cd792a28dcc55 upstream.

Completing aggregate frames can lead to new buffers being pushed into
the tid queues due to software retransmission.
When the tx queues are being drained, all pending aggregates must be
completed before the tid queues get drained, otherwise buffers might be
leaked.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>