[yocto] Removing builds of meta-fsl-* from the autobuilder

[Richard Purdie]

NXP has decided to lower its contributions to the support of the
project and is no longer eligible for the level of automated testing
we've been making of meta-fsl-ppc and meta-fsl-arm. As such we're going
to disable those builds going forward.

I don't like doing that but equally this does put a considerable load
on the infrastructure and the people running the builds and triaging
bugs and this is what we warned would have to happen.

Beth: Could you make the necessary changes please?

Richard