dell-laptop: touchpad LED should persist its status after S3

commit 2d5de9e8 upstream.

Touchpad LED will not turn on after S3, it will make the touchpad status
doesn't consist with the LED.
By adding one flag to let the LED device restore it's status.
Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/platform/x86/dell-laptop.c

@@ -642,6 +642,7 @@ static void touchpad_led_set(struct led_classdev *led_cdev,
 static struct led_classdev touchpad_led = {
 	.name = "dell-laptop::touchpad",
 	.brightness_set = touchpad_led_set,
+	.flags = LED_CORE_SUSPENDRESUME,
 };
 
 static int __devinit touchpad_led_init(struct device *dev)