ANDROID: KVM: On guest exit ask Trustzone to relinquish the borrowed pages

Iterate the list of handles which identify the shared memory regions and
relinquish them from Trustzone. Let the host call into the scheduler
before retrying to ask the hypervisor to reclaim Trustzone memory.

Bug: 269285339
Bug: 278749606
Change-Id: Ia0eae5109ab5ee3e47bed655a5ff51aae15129fc
Signed-off-by: Sebastian Ene <sebastianene@google.com>