AMD agesa family15: PCI domain should scan bus from 0x18.0

There are four mainboards using agesa family15 code:
Supermicro h8scm and h8qgi, Tyan s8226 and AMD dinar.
All of these boards' PCI domain starts from 0x18.0. Take h8scm as
an example, PCI devices from 0.0 to 0x14.5 is under 0x18.0.
Now, the PCI domain's scan bus function stats from 0.0. This would
result to the PCI devices be scanned twice. Because when the function
run to device 18.0, it would scan from 0.0 again.
This issue would result to 2 problems:
1) PCI device may be assigned two different PCI address.
   If this happenned on VGA device, coreboot maybe not load
   vga bios correctly.
2) coreboot initializes rd890's IO APIC twice.
So this patch scans from 0x18.0 and could resolve the problems above.

Change-Id: I90fbdf695413fd24c7a5e3e9b426dc7ca6e128b1
Signed-off-by: Siyuan Wang <SiYuan.Wang@amd.com>
Signed-off-by: Siyuan Wang <wangsiyuanbuaa@gmail.com>
Reviewed-on: http://review.coreboot.org/1639
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marcj303@gmail.com>
2 files changed