linux-postmarketos-allwinner: switch to mainline rtw88 driver

linux-postmarketos-allwinner kernel currently uses custom driver for wifi chip (/drivers/staging/rtl8723cs):

$ </proc/config.gz gunzip -d | grep -Ei 'RTL8723|RTW88'

# CONFIG_RTW88 is not set
CONFIG_RTL8723BS=m
CONFIG_RTL8723CS=m

$ lsmod | grep 8723

8723cs               1466368  0

anarsoul was fixing issues with mainline rtw88 driver and believes it is ready.

<anarsoul> hey folks
<anarsoul> just fyi, I fixed RX/TX performance issues with mainline rtw88_8723cs driver
<anarsoul> https://patchwork.kernel.org/project/linux-wireless/patch/20250103075107.1337533-1-anarsoul@gmail.com/
<anarsoul> megi: ^^
<a​narsoul> It'll make megi's life easier if he doesn't need to carry the vendor driver in his tree anymore :)
<a​narsoul> The source is available for the vendor driver, however it wasn't easy to find what was wrong with rtw88
<a​narsoul> The issue with the vendor driver is that it carries its own 802.11 stack and pretends to be a fullmac device
<a​narsoul> No one knows what vulnerabilities are there in their implementation of 802.11 stack
<a​narsoul> rtw88 does it properly and uses mac80211
<a​narsoul> That would definitely need some testing

Check if/when we can switch, either automatically if megi drops the custom driver, or manually.