rtw89: add addr_cam field to sta to support AP mode

In AP mode, each connected station needs an entry of address CAM. The
address CAM of vif is still needed to assit in AP itself.

For station mode, it still uses vif's address CAM.

Add a help macro rtw89_get_addr_cam_of() to get addr_cam from vif or sta
for all use cases.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220207063900.43643-3-pkshih@realtek.com