wifi: rtw89: pci: implement PCI mac_pre_init for WiFi 7 chips

Call this function when doing MAC initialization at probe stage. It does
partial initial registers only, because we only need basic ability to
download firmware. The function to clear index is the sub-function,
so set its pointer as well.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231101072149.21997-4-pkshih@realtek.com