perf cpumap: Use perf_cpu_map__cpu(map, cpu) instead of accessing map->map[cpu] directly

So that we can validate the 'map' instance wrt refcount checking.

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/lkml/20230407230405.2931830-3-irogers@google.com
[ Extracted from a larger patch ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/cpumap.c

@@ -582,26 +582,26 @@ size_t cpu_map__snprint(struct perf_cpu_map *map, char *buf, size_t size)
 		bool last = i == perf_cpu_map__nr(map);
 
 		if (!last)
-			cpu = map->map[i];
+			cpu = perf_cpu_map__cpu(map, i);
 
 		if (start == -1) {
 			start = i;
 			if (last) {
 				ret += snprintf(buf + ret, size - ret,
 						"%s%d", COMMA,
-						map->map[i].cpu);
+						perf_cpu_map__cpu(map, i).cpu);
 			}
-		} else if (((i - start) != (cpu.cpu - map->map[start].cpu)) || last) {
+		} else if (((i - start) != (cpu.cpu - perf_cpu_map__cpu(map, start).cpu)) || last) {
 			int end = i - 1;
 
 			if (start == end) {
 				ret += snprintf(buf + ret, size - ret,
 						"%s%d", COMMA,
-						map->map[start].cpu);
+						perf_cpu_map__cpu(map, start).cpu);
 			} else {
 				ret += snprintf(buf + ret, size - ret,
 						"%s%d-%d", COMMA,
-						map->map[start].cpu, map->map[end].cpu);
+						perf_cpu_map__cpu(map, start).cpu, perf_cpu_map__cpu(map, end).cpu);
 			}
 			first = false;
 			start = i;