wayland: treat touchpads like mouse devices

They both serve the same purpose of moving
the pointer around, so they both should be
considered pointer devices on the seat.

src/wayland/meta-wayland-seat.c

@@ -117,6 +117,7 @@ lookup_device_capabilities (ClutterDeviceManager *device_manager)
 
       switch (device_type)
         {
+        case CLUTTER_TOUCHPAD_DEVICE:
         case CLUTTER_POINTER_DEVICE:
           capabilities |= WL_SEAT_CAPABILITY_POINTER;
           break;