out from UCHIYAMA Yasushi's PCI BIOS patches, and fairly heavily reworked
by me.
Main differences:
- Only use the PCI BIOS to get the config mechanism and interrupt routing
info for now. No need to use the BIOS for PCI config access right now,
since the old mechanism works fine, and this keeps the code smaller.
- PCI BIOS initialization code path is much different.
- Always use the $PIR table if it exists, and only fallback to the
PCI BIOS 2.1 GetInterruptRouting call if it's not there.
This module does not include any of the fixup code; that is coming
in separate commits.
