freedreno: Enable piglit in CI.
Branch here. Currently takes down systems in CI, so we need to stabilize it first. Also check if there is low-hanging fruit for perf, as a quick_gl run is >7 minutes.
Notable issues from running piglit on debian a630:
- fbo-generatemipmap-formats -auto generates faults
- ext_framebuffer_multisample-* generates faults
- tex-miplevel-selection takes 9.5s for most of the tests.