wifi: ath9k: consistently use kstrtoX_from_user() functions

Use 'kstrtoul_from_user()' and 'kstrtobool_from_user()'
where appropriate and thus avoid some code duplication.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230726185046.188225-1-dmantipov@yandex.ru