platform/x86: asus-wmi: Fix hwmon device cleanup

The driver does not clean up the hwmon device on exit or error. To
reproduce the bug, repeat rmmod, insmod to verify that device number
/sys/devices/platform/asus-nb-wmi/hwmon/hwmon?? grows every time. Replace
call for registering device with devm_* version that unregisters it
automatically.
Signed-off-by: Yurii Pavlovskyi <yurii.pavlovskyi@gmail.com>
Reviewed-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/asus-wmi.c

@@ -1428,11 +1428,12 @@ __ATTRIBUTE_GROUPS(hwmon_attribute);
 
 static int asus_wmi_hwmon_init(struct asus_wmi *asus)
 {
+	struct device *dev = &asus->platform_device->dev;
 	struct device *hwmon;
 
-	hwmon = hwmon_device_register_with_groups(&asus->platform_device->dev,
-						  "asus", asus,
+	hwmon = devm_hwmon_device_register_with_groups(dev, "asus", asus,
 			hwmon_attribute_groups);
+
 	if (IS_ERR(hwmon)) {
 		pr_err("Could not register asus hwmon device\n");
 		return PTR_ERR(hwmon);