HID: multitouch: do not map usage from non used reports

hid-multitouch only handles touch events, so there is no point in
mapping other kind of events.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-multitouch.c

@@ -741,7 +741,7 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 	* such as Mouse that might have the same GenericDesktop usages. */
 	if (field->application != HID_DG_TOUCHSCREEN &&
 	    field->application != HID_DG_TOUCHPAD)
-		return 0;
+		return -1;
 
 	/* eGalax devices provide a Digitizer.Stylus input which overrides
 	 * the correct Digitizers.Finger X/Y ranges.