CI to stop testing meta-* layers not in tested machine

[Andrew Geissler]

I took an action item from last weeks Infrastructure Workgroup.

The point was we're wasting CI resources by testing meta-*
commits that are not actually tested by any of the machines in the
CI job. We're also falsely marking those commits as Verified because
if they are not in any of the systems under test, they're not being
tested at all.

The systems currently run as a part of the meta-* CI jobs are here:
https://openpower.xyz/view/CI/job/run-meta-ci/

Some quick grepping indicates the following meta-* repos are not
being tested:

meta-arm
meta-evb
meta-google
meta-hxt
meta-inspur
meta-intel
meta-inventec
meta-mellanox
meta-nuvoton
meta-portwell
meta-qualcomm
meta-quanta
meta-raspberrypi
meta-security
meta-x86
meta-xilinx

This would mean the maintainers of the above repos would need to +1
Verify the changes to these layers before merging.

Are there any advantages to running CI against meta-* layers that
are not in a machine being built? Are there other machines we can
add to CI that would cover some of the meta layers above? The
general criteria for getting a machine added to CI is that it's actively
being developed and supported. We also need to balance our
CI compute resources so the overall goal (in my mind) would be
to pick the machines that cover the most meta layers.

Andrew