Disable mmconfig on AMD CPUs.

This patch fixes various problems on PCI Express boards, like the
Nforce4. They have a MCFG table in ACPI, but not all devices can be
accessed using MMCONFIG.  e.g. the CPU builtin PCI devices in the A64
Northbridge can't.  Linux happily uses mmconfig for all PCI devices and
that cause failures and memory corruption.

Right solution apparently is to get more information from MCFG which is
supposed to tell for which busses mmconfig is legal and for which ones
not. But that would be a much more complicated patch and I don't have
a specification of this enhanced table.

This patch just disable MMCONFIG on all AMD CPUs. This is a kludge,
but works around the problem for now.

Patch for both i386 and x86-64
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>