evdev: restore EVDEV_UNHANDLED_DEVICE error code

If we don't have capabilities we can deal with, return a different error so
the backends can handle it separately (they already do).

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

src/evdev.c

@@ -668,6 +668,10 @@ err:
 	if (fd >= 0)
 		close_restricted(libinput, fd);
 	evdev_device_destroy(device);
+
+	if (device->seat_caps == 0)
+		return EVDEV_UNHANDLED_DEVICE;
+
 	return NULL;
 }