ANDROID: KVM: arm64: Move addr_is_allowed_memory() check into host callback

Since host stage-2 mappings are created lazily, we cannot rely on the
pte in order to recover the target physical address when checking a
host-initiated memory transition.

Instead, move the addr_is_allowed_memory() check into the host callback
function where it is passed the physical address directly from the
walker.

Bug: 279739439
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I84bdc43eded79f1f5e5a489dbc0874604491e5c8