ath9k: fix a potential buffer leak in the STA teardown path

ath9k: fix a potential buffer leak in the STA teardown path

commit 2b40994cabd2f545d5c11d3a65dcee6f6f9155f8 upstream.

It looks like it might be possible for a TID to be paused, while still
holding some queued buffers, however ath_tx_node_cleanup currently only
iterates over active TIDs.
Fix this by always checking every allocated TID for the STA that is being
cleaned up.

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>