ANDROID: KVM: arm64: Support pVM memory sharing with Trustzone(FF-A)

Store an annotation inside the guest stage-2 pagetables to mark the
memory as shared with FF-A. The memory transitions from the OWNED state
to
SHARED_OWNED. Return the PA corresponding to the page that
we want to share to prevent additional walks.

Bug: 269285339
Bug: 278749606
Change-Id: I5bdd51824ceffb4a891f2e97b62cc5af4460e542
Signed-off-by: Sebastian Ene <sebastianene@google.com>