perf/x86/intel/pebs: Fix PEBS timestamps overwritten

The PEBS TSC-based timestamps do not appear correctly in the final
perf.data output file from perf record.

The data->time field setup by PEBS in the setup_pebs_fixed_sample_data()
is later overwritten by perf_events generic code in
perf_prepare_sample(). There is an ordering problem.

Set the sample flags when the data->time is updated by PEBS.
The data->time field will not be overwritten anymore.

Reported-by: Andreas Kogler <andreas.kogler.0x@gmail.com>
Reported-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220901130959.1285717-3-kan.liang@linux.intel.com