sched/core: Merge cpumask_andnot()+for_each_cpu() into for_each_cpu_andnot()

This removes the second use of the sched_core_mask temporary mask.
Suggested-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>

kernel/sched/core.c

@@ -360,10 +360,7 @@ static void __sched_core_flip(bool enabled)
 	/*
 	 * Toggle the offline CPUs.
 	 */
-	cpumask_copy(&sched_core_mask, cpu_possible_mask);
-	cpumask_andnot(&sched_core_mask, &sched_core_mask, cpu_online_mask);
-
-	for_each_cpu(cpu, &sched_core_mask)
+	for_each_cpu_andnot(cpu, cpu_possible_mask, cpu_online_mask)
 		cpu_rq(cpu)->core_enabled = enabled;
 
 	cpus_read_unlock();