staging: comedi: 8255_pci: support memory mapped i/o boards

Some of the PCI based 8255 boards that can be supported by this driver
use memory mapped i/o. Add the code needed to support these boards.

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>