wifi: rtw88: use kstrtoX_from_user() in debugfs handlers

When 'sscanf()' is not needed to scan an input, prefer common
'kstrtoX_from_user()' over 'rtw_debugfs_copy_from_user()' with
following 'kstrtoX()'. Minor adjustments, compile tested only.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240110132930.438828-1-dmantipov@yandex.ru