[Buildroot] [PATCH 2/4] stm32mp157c_dk2: add non-trusted configuration

[Sergey Matyukevich <geomatsi@gmail.com>]

Hello Thomas,

> > The stm32mp157 supports two different boot chains. Trusted boot chain uses
> > TF-A firmare as FSBL and U-Boot as SSBL. Basic boot chain uses U-Boot SPL
> > as FSBL and U-Boot as SSBL. Available stm32mp157c_dk2_defconfig provides
> > image with trusted boot chain. This commit renames existing defconfig and
> > adds another defconfig for basic boot chain. Genimage template and
> > post-image script are modified to use appropriate FSBL and SSBL
> > to support both build configurations.
> 
> Could you comment on the motivation to also support the non-trusted
> boot chain? ST is no longer supporting the non-trusted configuration.
> Of course, while we don't have to strictly follow vendor-defined
> rules/decision, there's the question of what is the benefit of the
> non-trusted version, and if it's worth the effort having support for
> both configurations as Buildroot defconfigs.

Well, nothing specific. It just occured to me that there are not so many
boards supporting both TF-A and SPL boot options. But if vendor no
longer supports that configuration, then indeed that effort does not
make a lot of sense. I will drop that in v2.

Regards,
Sergey