[PATCH] powerpc: implement pcibus_to_node and pcibus_to_cpumask

On 64bit powerpc we can find out what node a pci bus hangs off, so
implement the topology.h macros that export this information.

For 32bit this seems a little more difficult, but I don't know of 32bit
powerpc NUMA machines either, so let's leave it out for now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>