implementation: update link to repo mainboards->linuxboot

[orangecms]

[rminnich]

I'd recommend we not do this. The move of mainboards to linuxboot was really half-assed and I am not sure what is in linuxboot is even right.

[orangecms]

Yea this whole project needs a lot of work, still. Having both repos was confusing, and neither is in great shape. I wouldn't state that keeping the link to the now-archived mainboard repo is ideal either.,,

I'm currently trying to get the linuxboot/linuxboot repo to a working state again, see https://github.com/linuxboot/linuxboot/pull/95