spapr-pci: remove io ports workaround

In the past, IO space could not be mapped into the memory address space
so we introduced a workaround for that. Nowadays it does not look
necessary so we can remove the workaround and make sPAPR PCI
configuration simplier.

This workaround has also an evil side effect with virtio devices: because
all PHBs have their .io region at the same address, the devices
get mapped in the .io-alias region of every PHB (AKA. mapped multiple times).
This breaks the ioeventfd feature and causes qemu to abort() when running
with KVM and asking for more than one PHB:

$ qemu-system-ppc64 -machine type=pseries,accel=kvm -smp 1 -m 4G \
  -hda /local/greg/images/fedora-be.qcow2 \
  -device virtio-9p-pci,fsdev=fsdev0,mount_tag=share,bus=pci,ioeventfd=on \
  -fsdev local,security_model=none,id=fsdev0,path=$HOME/share1 \
  -device spapr-pci-host-bridge,index=15
kvm_mem_ioeventfd_add: error adding ioeventfd: File exists
Aborted

This will prevent to use virtio and VFIO passthrough at the same time, since
VFIO needs a dedicated PHB to work on ppc.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>