Add "amdfam10" to the supported CPU types for amd64.  This complements
r251691 and 251692.
Make detaching drivers from PCI devices more robust.  While here, fix a
bug where a PCI device would be powered down if it failed to probe, but
not when its driver was detached (e.g. via kldunload).
- Add a new helper method resource_list_release_active() which forcefully
  releases any active resources of a specified type from a resource list.
- Add a bus_child_detached method for the PCI bus driver which forces any
  active resources to be released (and whines to the console if it finds
  any) and then powers the device down.
- Call pci_child_detached() if we fail to probe a device when a driver
  is kldloaded.  This isn't perfect but can avoid leaking resources
  from a probe() routine in the kldload case.

Reviewed by:	imp, brooks
MFC after:	1 month