staging: comedi: usbdux: remove unnecessary tidy_up() calls

If the comedi_driver (*auto_attach) fails, the comedi core will call
the (*detach) function to do any cleanup. It's not necessary to do
the cleanup in the (*auto_attach).

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>