wifi: rtw88: Add rtw8821cu chipset support

Add support for the rtw8821cu chipset based on
https://github.com/ulli-kroll/rtw88-usb.git



Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20221202081224.2779981-9-s.hauer@pengutronix.de