Adjust the global MSI blacklisting strategy so we don't have to explicitly
blacklist a bunch of old chipsets. If a system contains a PCI-PCI bridge
that supports PCI-X, assume the chipset supports PCI-X. If a system
contains a PCI-express root port, assume the chipset supports PCI-express.
If the chipset doesn't support either PCI-X or PCI-express, then blacklist
it by default. We should now only need to explicitly blacklist PCI-X or
PCI-express chipsets that don't properly handle MSI.