staging: comedi: addi_apci_2032: board does not have digital inputs

The board supported by this driver does not have digital inputs. Remove
the subdevice init for it.

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>