[POWERPC] Merge pci_process_bridge_OF_ranges()

This merges the 32-bit and 64-bit implementations of
pci_process_bridge_OF_ranges().  The new function is cleaner than both
the old ones, and supports 64 bits ranges on ppc32 which is necessary
for the 4xx port.

It also adds some better (hopefully) output to the kernel log which
should help diagnose problems and makes better use of existing OF
parsing helpers (avoiding a few bugs of both implementations along
the way).

There are still a few unfortunate ifdef's but there is no way around
these for now at least not until some other bits of the PCI code are
made common.

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