Add the gfx-pps backbone in `src/pps`.
v2: Simplify supported drivers creation.
v3: No default getter is provided for counters.
v4: Open DRM device in read/write mode.
v5: Wait for datasource to be started.
v6: Set FIFO scheduler while sampling counters.
Signed-off-by: Antonio Caggiano <antonio.caggiano@collabora.com>
Acked-by: Emma Anholt <emma@anholt.net>
Reviewed-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: John Bates <jbates@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9652>
