Add copyright notice on initramfs/rootfs scripts

Add SPDX-License-Identifier to scripts ...

Clarify the license of copyrighted works made by Xogium.
This deliberately excludes files that may not be copyrightable such as
purely informative files like hashes for packages, config values,
systemd units, and machine generated files.

board/MynaPlayer odyssey: only copy machine-id into the target with postbuild scripts. Use a device table file to alter its permissions later -- this avoids getting a permission denied error if you have to run the postbuild script multiple times e.g: build errors with trying multiple fixes.

Initial commit.