MFC 211820,211821,212292:
Intel QPI chipsets actually provide extra "non-core" PCI buses that
provide PCI devices for various hardware such as memory controllers,
etc. for each socket. These PCI buses are not enumerated via ACPI
however. Add qpi(4) psuedo bus and Host-PCI bridge drivers to
enumerate these buses. Currently the driver uses the CPU ID to
determine the bridges' presence.