soc: loongson: loongson_pm2: Populate children syscon nodes

The syscon poweroff and reboot nodes logically belong to the Power
Management Unit so populate possible children.

Without it, the reboot/poweroff feature becomes unavailable.
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/soc/loongson/loongson2_pm.c

@@ -11,6 +11,7 @@
 #include <linux/input.h>
 #include <linux/suspend.h>
 #include <linux/interrupt.h>
+#include <linux/of_platform.h>
 #include <linux/pm_wakeirq.h>
 #include <linux/platform_device.h>
 #include <asm/bootinfo.h>
@@ -192,6 +193,11 @@ static int loongson2_pm_probe(struct platform_device *pdev)
 	if (loongson_sysconf.suspend_addr)
 		suspend_set_ops(&loongson2_suspend_ops);
 
+	/* Populate children */
+	retval = devm_of_platform_populate(dev);
+	if (retval)
+		dev_err(dev, "Error populating children, reboot and poweroff might not work properly\n");
+
 	return 0;
 }