perf pmu: Use perf_cpu_map__set_nr() in perf_pmu__cpus_match() to allow for refcnt checking

One more step to allow for checking reference counting, user after free,
etc.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Riccardo Mancini <rickyman7@gmail.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>
Link: https://lore.kernel.org/ZDb9dycHQ11UIXwx@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>