[POWERPC] Merge PCI resource allocation & assignment

The 32 bits PCI code now uses the generic code for assigning unassigned
resources and an algorithm similar to x86 for claiming existing ones.

This works far better than the 64 bits code which basically can only
claim existing ones (pci_probe_only=1) or would fall apart completely.

This merges them so that the new 32 bits implementation is used for both.

64 bits now gets the new PCI flags for controlling the behaviour, though
the old pci_probe_only global is still there for now to be cleared if you
want to.

I kept a pcibios_claim_one_bus() function mostly based on the old 64
bits code for use by the DLPAR hotplug. This will have to be cleaned
up, thought I hope it will work in the meantime.

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