ANDROID: KVM: arm64: Donate IOMMU regions to pKVM

The MMIO register space for IOMMUs controlled by the hypervisor is
currently unmapped from the host stage-2, and we rely on the host abort
path to not accidentally map them. However, this approach becomes
increasingly difficult to maintain as we introduce support for donating
MMIO regions and not just memory -- nothing prevents the host from
donating a protected MMIO register to another entity for example.

Now that MMIO donations are possible, let's use the proper
host-donate-hyp machinery to implement this. As a nice side effect, this
guarantees the host stage-2 page-table is annotated with hyp ownership
for those IOMMU regions, which guarantees the core range alignment
feature in the host mem abort parth will do the right thing without
requiring a second pass in the IOMMU code. This also turns the host
stage-2 PTEs into "non-default" entries, hence avoiding issues with the
coallescing code looking forward.

Bug: 264070847
Change-Id: I1fad1b1be36f3b654190a912617e780141945a8f
Signed-off-by: Quentin Perret <qperret@google.com>