wifi: rtw89: mac: move code related to hardware engine to individual functions

WiFi 7 chips will use the same functionalities but different registers to
control hardware components, so move these stuff into functions, and then
we can implement these for WiFi 7 chips later. This patch doesn't change
logic.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231124071703.132549-7-pkshih@realtek.com