staging: comedi: usbduxsigma: remove SUBDEV_* defines

The SUBDEV_* defines are only used during the (*auto_attach). Remove
the defines and just open code the values.

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>