hw/pci: modify pci_setup_iommu() to set PCIIOMMUOps

This patch modifies pci_setup_iommu() to set PCIIOMMUOps
instead of setting PCIIOMMUFunc. PCIIOMMUFunc is used to
get an address space for a PCI device in vendor specific
way. The PCIIOMMUOps still offers this functionality. But
using PCIIOMMUOps leaves space to add more iommu related
vendor specific operations.

Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: Yi Sun <yi.y.sun@linux.intel.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Hervé Poussineau <hpoussin@reactos.org>
Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Cc: BALATON Zoltan <balaton@eik.bme.hu>
Cc: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Cc: Jagannathan Raman <jag.raman@oracle.com>
Cc: Matthew Rosato <mjrosato@linux.ibm.com>
Cc: Eric Farman <farman@linux.ibm.com>
Cc: Halil Pasic <pasic@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Helge Deller <deller@gmx.de>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
[ clg: - refreshed on latest QEMU
       - included hw/remote/iommu.c
       - documentation update
       - asserts in pci_setup_iommu()
       - removed checks on iommu_bus->iommu_ops->get_address_space
       - included Elroy PCI host (PA-RISC) ]
Signed-off-by: Cédric Le Goater <clg@redhat.com>