gallium: add PIPE_CAP_MAX_COMBINED_HW_ATOMIC_COUNTER{S,_BUFFERS}

gallium: add PIPE_CAP_MAX_COMBINED_HW_ATOMIC_COUNTER{S,_BUFFERS}

This moves the evergreen-specific max-sizes out as a driver-cap, so
other drivers with less strict requirements also can use hw-atomics.

Remove ssbo_atomic as it's no longer needed.

We should now be able to use hw-atomics for some stages and not for
other, if needed.

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>