convert license headers to SPDX

Includes license review of 3rd-party files, adding missing upstream
headers, and moving the UNSW OZPLB license into its own file rather
than replicating it in the header.

pragma once and for all

Fix licenses

elfloader: Remove unnecessary 32 folder from armv6 and armv7 folders

elfloader: create the version dependant folders
- move the files to respective folder
- add machine.h for each version
- move cpu_idle to idle.c