[PATCH] powerpc: Workaround for offb on 64 bits platforms

This fixes a problem with offb not parsing addresses properly on 64 bits
machines, and thus crashing at boot.  The problem is worked around by
locating the matching PCI device and using the properly relocated PCI
base addresses instead of misparsing the Open Firmware properties.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>