Input: wacom - register power device at the HID level

Use the HID device as the parent for the power device when dealing with
a wireless receiver.
Removes one more usb dependency and does not break user space.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Reviewed-by: Jason Gerecke <killertofu@gmail.com>
Tested-by: Jason Gerecke <killertofu@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/tablet/wacom_sys.c

@@ -966,12 +966,12 @@ static int wacom_initialize_battery(struct wacom *wacom)
 		wacom->battery.type = POWER_SUPPLY_TYPE_BATTERY;
 		wacom->battery.use_for_apm = 0;
 
-		error = power_supply_register(&wacom->usbdev->dev,
+		error = power_supply_register(&wacom->hdev->dev,
 					      &wacom->battery);
 
 		if (!error)
 			power_supply_powers(&wacom->battery,
-					    &wacom->usbdev->dev);
+					    &wacom->hdev->dev);
 	}
 
 	return error;