perf/x86/intel/ds: Factor out functions for PEBS records processing

Factor out functions to process normal and the last PEBS records, which
can be shared with the later patch.

Move the event updating related codes (intel_pmu_save_and_restart())
to the end, where all samples have been processed.
For the current usage, it doesn't matter when perf updates event counts
and reset the counter. Because all counters are stopped when the PEBS
buffer is drained.
Drop the return of the !intel_pmu_save_and_restart(event) check. Because
it never happen. The intel_pmu_save_and_restart(event) only returns 0,
when !hwc->event_base or the period_left > 0.
- The !hwc->event_base is impossible for the PEBS event, since the PEBS
  event is only available on GP and fixed counters, which always have
  a valid hwc->event_base.
- The check only happens for the case of non-AUTO_RELOAD and single
  PEBS, which implies that the event must be overflowed. The period_left
  must be always <= 0 for an overflowed event after the
  x86_pmu_update().

Co-developed-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
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/20241119135504.1463839-4-kan.liang@linux.intel.com