pcibus and pci.
(2) remove the #ifdef i386 from pci.c, and provide a machine-dependent
hook (pci_md_attach_hook()) to do any machine-dependent attachment
gunk, e.g. on the i386 printing out the configuration mode (if bus 0)
(3) don't pass max device number for a given bus in, use
PCI_MAX_DEVICE_NUMBER, which can be defined on a per-machine basis.
(defaults to 32. on i386, it's 32 if pci conf mode == 1, 16 if 2.)
and attach the secondary pci bus as a 'pci' device. Note that this support
is incomplete and will not yet work for ports other than that i386. (The
i386 can rely on the PCI interrupt 'line' information to determine
interrupt mapping, which is not necessarily possible on other systems.)
