perf stat: No need to setup affinities when starting a workload

perf stat: No need to setup affinities when starting a workload

I.e. the simple:

  $ perf stat sleep 1

Uses a dummy CPU map and thus there is no need to setup/cleanup
affinities to avoid IPIs, etc.

With this we're down to a sched_getaffinity() call, in the libnuma
initialization, that probably can be removed in a followup patch.

Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20220117160931.1191712-3-acme@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>