x86/PCI: host mmconfig detect clean up

x86/PCI: host mmconfig detect clean up

Fix mmconfig detection to not assume a single mmconfig space in the
northbridge, paving the way for AMD fam10h + mcp55 CPUs.  On those, the
MSR has some range, but the mcp55 pci config will have another one.

Also helps the mcp55 + io55 case, where every one will have one range.

If it is mcp55, exclude the range that is used by CPU MSR, in other
words , if the CPU claims busses 0-255, the range in mcp55 is dropped,
because CPU HW will not route those ranges to mcp55 mmconfig to handle
it.

Signed-off-by: Yinghai Lu <yinghai.lu@kernel.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>