intel_iommu: Implement [set|unset]_iommu_device() callbacks

intel_iommu: Implement [set|unset]_iommu_device() callbacks

Implement [set|unset]_iommu_device() callbacks in Intel vIOMMU.
In set call, we take a reference of HostIOMMUDevice and store it
in hash table indexed by PCI BDF.

Note this BDF index is device's real BDF not the aliased one which
is different from the index of VTDAddressSpace. There can be multiple
assigned devices under same virtual iommu group and share same
VTDAddressSpace, but each has its own HostIOMMUDevice.

Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Yi Sun <yi.y.sun@linux.intel.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>