wifi: rtw89: mac: use pointer to access functions of hardware engine and quota

To share flow with WiFi 7 chips, abstract functions related hardware
engines and their quota, so use pointer to access them. This 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://lore.kernel.org/r/20231124071703.132549-8-pkshih@realtek.com