hw/pci: Introduce helper function pci_device_get_iommu_bus_devfn()

Extract out pci_device_get_iommu_bus_devfn() from
pci_device_iommu_address_space() to facilitate
implementation of pci_device_[set|unset]_iommu_device()
in following patch.

No functional change intended.

Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
1 file changed