A long time ago we renamed the flash_system action into flash_rootfs.
Since we still kept some variables around, it's finally time to clean
that up.
Keep backwards compatibility for now since we cannot update pmaports at
the same time since the new deviceinfo names won't be supported in older
pmbootstrap versions.
Reviewed-by: Oliver Smith <ollieparanoid@postmarketos.org>
Link: https://lists.sr.ht/~postmarketos/pmbootstrap-devel/%3C20230605220329.14328-3-luca@z3ntu.xyz%3E