staging: comedi: addi_apci_1032: only allocate one subdevice

There is only one subdevice used in the driver. Remove the unused
subdevice init and only allcoate space for the one used.

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