HID: wacom: remove the extra Pen interface for Wacom Bamboo PAD

As mentioned in the comment in the code, both the pen and touch data
come from the interface tagged as BAMBOO_PAD. The driver re-routes the
events for the Pen to the generic HID interface and keeps the ones for
the touch through this current interface.

Clearing the WACOM_DEVICETYPE_PEN bit removes the extra unused interface
added in 2a6cdbdd ("HID: wacom: Introduce new 'touch_input' device") and
makes the Bamboo PAD to behave like in 4.1.
Reviewed-by: Jason Gerecke <jason.gerecke@wacom.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

drivers/hid/wacom_wac.c

@@ -2220,10 +2220,10 @@ void wacom_setup_device_quirks(struct wacom *wacom)
 	 * 0, whose HID descriptor has an application usage of 0xFF0D
 	 * (i.e., WACOM_VENDORDEFINED_PEN). We route pen packets back
 	 * out through the HID_GENERIC device created for interface 1,
-	 * so rewrite this one to be of type BTN_TOOL_FINGER.
+	 * so rewrite this one to be of type WACOM_DEVICETYPE_TOUCH.
 	 */
 	if (features->type == BAMBOO_PAD)
-		features->device_type |= WACOM_DEVICETYPE_TOUCH;
+		features->device_type = WACOM_DEVICETYPE_TOUCH;
 
 	if (wacom->hdev->bus == BUS_BLUETOOTH)
 		features->quirks |= WACOM_QUIRK_BATTERY;