jasmine_sprout: new device (Xiaomi Mi A2)

This MR adds initial support for Xiaomi Mi A2 (jasmine_sprout).

Working:

• Display
• Touchscreen
• USB networking

Untested:

• Everything else

Install process still needs to be updated on the wiki.

1. zap & reinit pmbootstrap (pmbootstrap -y zap ; pmbootstrap init), choose vendor xiaomi and device jasmine_sprout
2. proceed with installation as usual: reboot device to fastboot mode, then:

• pmbootstrap install
• pmbootstrap flasher flash_kernel
• pmbootstrap flasher flash_rootfs
• pmbootstrap flasher flash_vbmeta

3. fastboot reboot