pseries: Add partial support for PCI

pseries: Add partial support for PCI

This patch adds a PCI bus to the pseries machine.  This instantiates
the qemu generic PCI bus code, advertises a PCI host bridge in the
guest's device tree and implements the RTAS methods specified by PAPR
to access PCI config space.  It also sets up the memory regions we
need to provide windows into the PCI memory and IO space, and
advertises those to the guest.

However, because qemu can't yet emulate an IOMMU, which is mandatory on
pseries, PCI devices which use DMA (i.e. most of them) will not work with
this code alone.  Still, this is enough to support the virtio_pci device
(which probably _should_ use emulated PCI DMA, but is specced to use
direct hypervisor access to guest physical memory instead).

[agraf] remove typedef which could cause compile errors

Signed-off-by: Alexey Kardashevskiy <aik@au1.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>