perf affinity: Allow passing a NULL arg to affinity__cleanup()

Just like with free(), NULL is checked to avoid having all callers do
it.

Its convenient for when not using affinity setup/cleanup for dummy CPU
maps, i.e. CPU maps for pid targets.
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/20220117160931.1191712-2-acme@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/affinity.c

@@ -62,7 +62,7 @@ void affinity__set(struct affinity *a, int cpu)
 	clear_bit(cpu, a->sched_cpus);
 }
 
-void affinity__cleanup(struct affinity *a)
+static void __affinity__cleanup(struct affinity *a)
 {
 	int cpu_set_size = get_cpu_set_size();
 
@@ -71,3 +71,9 @@ void affinity__cleanup(struct affinity *a)
 	zfree(&a->sched_cpus);
 	zfree(&a->orig_cpus);
 }
+
+void affinity__cleanup(struct affinity *a)
+{
+	if (a != NULL)
+		__affinity__cleanup(a);
+}