while after the legacy device was added since this driver hangs from
legacy and not nexus.
- Make several methods non-static so they can be reused in a mptable
host -> pci bridge driver that will be added at a later date.
- Let legacy_pcib() use pcibios_pcib_route_interrupt() directly instead of
wrapping it in a private function. Originally, I thought I was going to
have the nexus_pcib() driver make a runtime APIC vs. 8259A check and call
the appropriate routing method (MPTable vs. PIR) that way, but it ended
up being cleaner to make nexus_pcib() just work with PIR and have a
separate host -> pci bridge driver for the mptable/apic case.
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