Draft: msm89x7: Add mainline kernel and devices

This MR is for testing purpose for msm89x7 devices. New Packages:

• linux-postmarketos-qcom-msm89x7

New Devices:

• xiaomi-land
• xiaomi-ugg
• xiaomi-ugglite

Ported from downstream:

• xiaomi-santoni
• xiaomi-riva

TODO:

• make a stable branch at the kernel fork
• clean up the packages
• clarify the maintainers (are the old maintainers still active, is there anyone who want to be a maintainer)
• Add motorola-montana
• Add lk2nd-msm8952 as a new package and dependency