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 <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/affinity.c

···
 	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();
 
···
 		sched_setaffinity(0, cpu_set_size, (cpu_set_t *)a->orig_cpus);
 	zfree(&a->sched_cpus);
 	zfree(&a->orig_cpus);
+}
+
+void affinity__cleanup(struct affinity *a)
+{
+	if (a != NULL)
+		__affinity__cleanup(a);
 }