iommu/s390: Implement blocking domain

In the Linux kernel, the following vulnerability has been resolved:

iommu/s390: Implement blocking domain

This fixes a crash when surprise hot-unplugging a PCI device. This crash

happens because during hot-unplug __iommu_group_set_domain_nofail()

attaching the default domain fails when the platform no longer

recognizes the device as it has already been removed and we end up with

a NULL domain pointer and UAF. This is exactly the case referred to in

the second comment in __iommu_device_set_domain() and just as stated

there if we can instead attach the blocking domain the UAF is prevented

as this can handle the already removed device. Implement the blocking

domain to use this handling. With this change, the crash is fixed but

we still hit a warning attempting to change DMA ownership on a blocked

device.