ANDROID: KVM: arm64: Allow state changes of MMIO pages

We've historically disallowed state changes for MMIO pages -- the host
had sole ownership of all of them. However, changing the state of those
pages has clearly become a goal both to support vendor extensions to
the hypervisor, as well as to support device assignment in the longer
term. To pave the way towards this support, let's allow certain state
transitions for MMIO pages.

Bug: 264070847
Change-Id: I9803b572c90d8a694c3d43a0ee0d7b4f4124fe4a
Signed-off-by: Quentin Perret <qperret@google.com>