intel/perf: take into account that reports read can be fairly old

intel/perf: take into account that reports read can be fairly old

If we read the OA reports late enough after the query happens, we can
get a timestamp in the report that is significantly in the past
compared to the start timestamp of the query. The current code must
deal with the wraparound of the timestamp value (every ~6 minute). So
consider that if the difference is greater than half that wraparound
period, we're probably dealing with an old report and make the caller
aware it should read more reports when they're available.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Mark Janes <mark.a.janes@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>