wifi: rtw89: mac: add suffix _ax to MAC functions

Many existing MAC access functions are used by WiFi 6 chips only, so add
suffix _ax to be clearer. Some are common and can be used by WiFi 7, so
export this kind of functions. This patch doesn't change logic at all.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20231211083341.118047-5-pkshih@realtek.com