leds: Use vtime aware kcpustat accessor to fetch CPUTIME_SYSTEM

Now that we have a vtime safe kcpustat accessor for CPUTIME_SYSTEM, use
it to start fixing frozen kcpustat values on nohz_full CPUs.

Reported-by: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J . Wysocki <rjw@rjwysocki.net>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Wanpeng Li <wanpengli@tencent.com>
Link: https://lkml.kernel.org/r/20191016025700.31277-15-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

drivers/leds/trigger/ledtrig-activity.c

@@ -59,7 +59,7 @@ static void led_activity_function(struct timer_list *t)
 	for_each_possible_cpu(i) {
 		curr_used += kcpustat_cpu(i).cpustat[CPUTIME_USER]
 			  +  kcpustat_cpu(i).cpustat[CPUTIME_NICE]
-			  +  kcpustat_cpu(i).cpustat[CPUTIME_SYSTEM]
+			  +  kcpustat_field(&kcpustat_cpu(i), CPUTIME_SYSTEM, i)
 			  +  kcpustat_cpu(i).cpustat[CPUTIME_SOFTIRQ]
 			  +  kcpustat_cpu(i).cpustat[CPUTIME_IRQ];
 		cpus++;