device: Don't throw NXIO file error in *_new() if not a gamepad
NXIO has a specific use case, that is, No such device or address, and isn't meant for general-purpose use. Since there isn't any G_FILE_ERROR_NOT_A_GAME_CONTROLLER, use G_FILE_ERROR_FAILED which is made to be used when no unix error code exists for it.
Splitting from !48 (closed).