xiaomi-elish: new device (Xiaomi Pad 5 Pro)

I have made xiaomi-elish running mainline kernel, now I want to make it into pmaports. Here is the wiki of xiaomi-elish. https://wiki.postmarketos.org/wiki/Xiaomi_Mi_Pad_5_Pro_(xiaomi-elish)

Initial function works:

• USB networking
• Flashing
• Booting
• Backlight
• Battery fuel gauge