Fix regression introduced by commit 
143d9d9616 ("USB: serial: add
tiocmiwait subdriver operation") which made the ioctl operation return
ENODEV rather than ENOIOCTLCMD when a subdriver TIOCMIWAIT
implementation is missing.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
                                        unsigned int cmd, unsigned long arg)
 {
        struct usb_serial_port *port = tty->driver_data;
-       int retval = -ENODEV;
+       int retval = -ENOIOCTLCMD;
 
        dev_dbg(tty->dev, "%s - cmd 0x%.4x\n", __func__, cmd);
 
        default:
                if (port->serial->type->ioctl)
                        retval = port->serial->type->ioctl(tty, cmd, arg);
-               else
-                       retval = -ENOIOCTLCMD;
        }
 
        return retval;