wifi: rtw89: 8851b: add 8851be to Makefile and Kconfig

Since 8851BE is ready, so add 8851BE to Makefile and Kconfig. Currently,
it can support STA, AP and monitor modes with good performance.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230519031500.21087-8-pkshih@realtek.com