wifi: ath9k: cleanup ath_txq_skb_done()

wifi: ath9k: cleanup ath_txq_skb_done()

Since 'txq' argument of 'ath_txq_skb_done()' is actually
(mis|un)used, convert the former to local variable and
adjust all related users. Compile tested only.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Link: https://patch.msgid.link/20241209155027.636400-1-dmantipov@yandex.ru
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>