virtio-iommu: Compute host reserved regions

virtio-iommu: Compute host reserved regions

Compute the host reserved regions in virtio_iommu_set_iommu_device().
The usable IOVA regions are retrieved from the HostIOMMUDevice.
The virtio_iommu_set_host_iova_ranges() helper turns usable regions
into complementary reserved regions while testing the inclusion
into existing ones. virtio_iommu_set_host_iova_ranges() reuse the
implementation of virtio_iommu_set_iova_ranges() which will be
removed in subsequent patches. rebuild_resv_regions() is just moved.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>