sched/fair: use lsub_positive in cpu_util_next()

The sub_positive local version is saving an explicit load-store and is
enough for the cpu_util_next() usage.

Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Quentin Perret <qperret@google.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20210225083612.1113823-3-vincent.donnefort@arm.com

kernel/sched/fair.c

@@ -6471,7 +6471,7 @@ static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
 	 * util_avg should already be correct.
 	 */
 	if (task_cpu(p) == cpu && dst_cpu != cpu)
-		sub_positive(&util, task_util(p));
+		lsub_positive(&util, task_util(p));
 	else if (task_cpu(p) != cpu && dst_cpu == cpu)
 		util += task_util(p);