start of some pci cleanups

[Dave Airlie]

This is a first patch that cleans up some PCI interfaces, we don't
have any idea about domains at the normal level of the driver, I think
we should at least add the idea.

http://people.freedesktop.org/~airlied/change_pci_interface.diff

This just adds pci domain to the pcibusid struct and passes the
PciBusId struct around instead of passing bus,dev,func triplets.

For my next trick, I'd like to fix the xf86MapPciMem entry point to
take a pciVideoPtr, so that we can figure out the file in
/proc/bus/pci or /sys on Linux that is needed and mmap it rather than
using /dev/mem which is something that I'd like to stop doing.

Dave.