Updates to match changes elsewhere in the PCI subsystem:

Updates to match changes elsewhere in the PCI subsystem:

 - Remove redundant header-type-specific support in the cardbus pcibus
   clone.  The bridges don't need this anymore.
 - Use pcib_get_bus instead of the deprecated pci_get_secondarybus.
 - Implement read/write ivar support for the pccbb, and teach it how
   to report its secondary bus number.  Save the subsidiary bus number
   as well, although we don't use it yet.