staging: comedi: 8255_pci: use pci_ioremap_bar()

Use pci_ioremap_bar() to ioremap the PCI resources. That function
just takes the pci device and a bar number. It also has some
additional sanity checks to make sure the bar is actually a
memory resource.

Refactor the code a bit. The dev->iobase only needs to be set
when the board does not use memory mapped I/O. And the 'iobase'
passed to subdev_8255_init() is an unsigned long.

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>