wifi: ath9k: use devm for gpio_request_one()

Using devm_gpio_request_one() is simpler as then we don't need to call
gpio_free().

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://patch.msgid.link/20240731210312.7622-1-rosenp@gmail.com