intel_perf_counters: a little tool for dumping performance counters.

intel_perf_counters: a little tool for dumping performance counters.

This reads the GPU's performance counters via MI_REPORT_PERF_COUNT and
prints them in a top-style interface.  While it can be useful in and of
itself, it also documents the performance counters and lets us verify
that they're working.

Currently, it only supports Ironlake.

v2 [Ken]: Rebase on master and fix compilation failures; make it abort
on non-Ironlake platforms to avoid GPU hangs; rename from 'chaps' to
intel_perf_counters since that acronym isn't used any longer; write the
above commit message.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>