To be honest, I have no idea what I was smoking when I wrote this
originally, and it's kind of coincidental that it works at all currently.

We never use physical apicids after the cpus are all booted, so we should
just store the logical IDs which all subsequent things use. The only things
that were using the apicid->cpu mapping were hokey anyway, and it's hard to
maintain for machines that have a large apic addressing space (eg P4s
in clustered mode). Rips out everything except the mapping from
logical_apic_id -> cpu.