ANDROID: KVM: arm64: Add a MMIO flag for pKVM page state

Introduce a new pKVM meta-state for mappings with the MMIO guard
annotation.

Using a bit for that meta-state allow to distinguish between unmapped
and unmapped+annotation states while making it easy to write a filter
for the guest mem transition walker.

Bug: 278749606
Bug: 243642516
Change-Id: I5e66a48b44f5d22d1b3c80abecf4a6b424826ffe
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>