v2020: Fix the first stage config in a few other places

There are a couple of remaining locations where the first stage config need to be updated as done in the previous commit:

• common-minnowboard-boot-tpl.yaml which is specifically for the Minnowboard devices
• minimal-boot-tpl.yaml which is a test profile, to be used manually by developers and not part of any CI

See also https://gitlab.apertis.org/pkg/development/apertis-tests/-/merge_requests/206 for v2019.

Test run here: https://lava.collabora.co.uk/scheduler/job/2571286