Overriding pci_conf_interrupt

So, arch/powerpc/ibm4xx/pci/pci_machdep.c provides a pci_conf_interrupt,
and a pci_intr_map, which do not work on the TAMS 3011.

I am thinking that the right thing to do is split this into something like
	arch/powerpc/ibm4xx/pci/pci_cpudep.c
which provides the rest of the file, and
	arch/evbppc/*/pci_machdep.c
which provides the versions used by each target board.

Is this a sane approach?  The main thing that bothers me is that the others
all use the same form.  Maybe it ought to be
	arch/powerpc/ibm4xx/pci/pci_default.c
for the interrupt assignments that are shared by the other boards.

-s