PCI enhancements.

PCI enhancements.

Allow one to enable/disable PIR tables separately from PCI BIOS support.
Use standard PORT_* defs for 0xcf8/0xcfc port accesses.
Don't pass PCIDevice pointers around - the struct is small enough to
    pass in a register.
Extract out pci_find_device and pci_find_class functions from PCI BIOS
    code.
Remove PCI_FIXED_HOST_BRIDGE check - the check is too late if standard
    PCI support isn't available.  If standard support is available,
    then the code should be okay to run.