fixup_pci: Remove unused attach DEVMETHOD

The probe routine always fails, so the attach routine is unused.
However, this weird driver is really a quirk system for PCI and should
be turned into PCI quirks instead. The Natoma quirk is also broken as
it should be doing a runtime check either on mp_ncpus (or more likely
to see if it is using APIC) instead of #ifdef.

Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D47219