staging: comedi: 8255_pci: check BAR resource type directly

This driver handles one or more 8255 DIO subdevices mapped contiguously
at the start of a PCI BAR resource.  The resource may be a portio
resource or an mmio resource.  The driver currently checks the `is_mmio`
member of the matching element of `pci_8255_boards[]` to determine the
type of resource.  Rather than doing that, get the information straight
from the horse's mouth by checking the resource flags of the PCI BAR
and eliminate the `is_mmio` member.

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