ANDROID: KVM: arm64: Introduce module-owned pages

In order to let vendor pKVM modules change the permission of host pages,
introduce a new concept of module-owned pages. This flag is stored in
the vmemmap so it can be set for pages that have been unmapped from the
host and for which the stage-2 PTEs are invalid.

Bug: 264070847
Change-Id: Ic831d3873cf7d31a2bd9f411306d657cc2f4db01
Signed-off-by: Quentin Perret <qperret@google.com>