power: reset: sc27xx: Change to use cpu_down()

To allow the SC27XX driver can be built as a module, and the
freeze_secondary_cpus() symbol is not exported, thus we can change
to use the exported cpu_down() API to shut down other cpus to avoid
racing, which is same as the freeze_secondary_cpus().
Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/reset/sc27xx-poweroff.c

@@ -29,10 +29,13 @@ static struct regmap *regmap;
  */
 static void sc27xx_poweroff_shutdown(void)
 {
-#ifdef CONFIG_PM_SLEEP_SMP
-	int cpu = smp_processor_id();
+#ifdef CONFIG_HOTPLUG_CPU
+	int cpu;
 
-	freeze_secondary_cpus(cpu);
+	for_each_online_cpu(cpu) {
+		if (cpu != smp_processor_id())
+			cpu_down(cpu);
+	}
 #endif
 }