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.

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