ANDROID: KVM: Prevent memory sharing outside of the RAM regions

Verify the address to be shared and prevent MMIO page
sharing. Allow MMIO to be donated to the hypervisor and
to the guest for device assignment.

Bug: 439996285
Signed-off-by: Sebastian Ene <sebastianene@google.com>

Cleaned up host_check_page_state_flags.

Change-Id: I98590534865d3239911350736831b8564d614fef
Signed-off-by: Keir Fraser <keirf@google.com>
(cherry picked from commit 33eb6bde)
Signed-off-by: Lee Jones <joneslee@google.com>