staging: comedi: addi_apci_3xxx: remove 'iobase' from private data

The private data 'iobase' is the same as the comedi_device 'iobase'.
Use the one in the comedi_device instead.

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