MFC: Replace remaining cpu_vendor with cpu_vendor_id and
add basic VIA Nano processor support for amd64 and i386.
r186797 - Add Centaur/IDT/VIA vendor ID for Nano family.
r187101 - Allow VIA Nano processors to boot FreeBSD/amd64.
r187117 - Replace more cpu_vendor with cpu_vendor_id.
r187118 - Add basic i386 support for VIA Nano processors.
r187157 - Enable MSI support for VIA Nano processors on i386.
r187594 - Replace more cpu_vendor with cpu_vendor_id.
r187597 - Include a missing header file.
r187598 - VIA Nano processor has P-state invariant TSC.
r187633 - Add more VIA bridges to agp_via.c.