Add Khadas VIM3 support

[agners]

Add sound configuration for Khadas VIM3. Currently only HDMI supported.
This requires access to device tree in sysfs.

[pvizeli]

That will not work because it's mask by docker. We Can pass the machine type over env

[agners]

Yes I realized, that is why I set it to draft 😅

We could also enable device tree access for Audio with a Supervisor upgrade I guess? Add-ons have that as an option. Not sure what is better/easier.

[agners]

Hm, I see there is currently not a easy way to access the firmware directory in its default location. /proc/device-tree symlinks to /sys/firmware/devicetree/base and /sys/firmware/` directory is in a hard-coded mask list since years: moby/moby@8b1772c

We support non-native location with this pull request: home-assistant/supervisor#519

It seems that a bind mount to a different location works, but the symlink /proc/device-tree can't be changed, so whereever we bind mount it would be non-standard :(

[agners]

New version using sound device id from sysfs.