kvm tools: Add PPC64 PCI Host Bridge

This provides the PCI bridge, definitions for the address layout of the windows
and wires in IRQs.  Once PCI devices are all registered, they are enumerated and
DT nodes generated for each.

Signed-off-by: Matt Evans <matt@ozlabs.org>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Pekka Enberg <penberg@kernel.org>