Merge branch '2023-04-25-use-bounce-buffers-for-VIRTIO_F_IOMMU_PLATFORM'

To quote the author:
These patches will use bounce buffers when VIRTIO_F_IOMMU_PLATFORM
feature is in a virtio device.

This feature can be tested with qemu with -device virtio-iommu-pci.  So
that when a -device virtio-blk-pci with iommu_platform=true, it will
uses the bounce buffer instead.