staging: comedi: usbduxsigma: removing unneccesay attached info

Comedi core now reports that a device has been attached so that
the driver itself won't need to do it any longer. The driver now
just outputs the offset of the ADC converter which is a soft indicator
of the health of the board and also the user can grep this value
from the kernel log easier for debugging purposes.

Signed-off-by: Bernd Porr <mail@berndporr.me.uk>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>