libperf: Fix perf_cpu_map__for_each_cpu macro

Tzvetomir Stoyanov reported an issue with using macro
perf_cpu_map__for_each_cpu using private perf_cpu object.

The issue is caused by recent change that wrapped cpu in struct perf_cpu
to distinguish it from cpu indexes. We need to make struct perf_cpu
public.

Add a simple test for using the perf_cpu_map__for_each_cpu macro.

Fixes: 6d18804b

 ("perf cpumap: Give CPUs their own type")
Reported-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20220215153713.31395-1-jolsa@kernel.org


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