OOP speak, you would mark these as 'protected' members. Specifically:
- Make the pcib_softc struct public so it can be used by subclasses.
- Make pcib_{read,write}_ivar(), pcib_alloc_resource(), pcib_maxslots(),
and pcib_{read,write}_config() globals that can be used by subclasses.
- Make the pcib devclass a global variable.
- Move most of the pcib_attach() function into a global
pcib_attach_common() function that can be called by the attach routines
of subclasses.
Tested on: i386, alpha, sparc64, ia64
