ANDROID: KVM: arm64: Reland split the host ffa handle store

Reserve an ffa handle entry before we commit the memory transfer to
TZ to avoid rolling back the memory transaction with TZ in case we
have no space the accomodate the handle.

Bug: 440584506
Bug: 357781595
Fixes: Ifbdc82adb2675f5e7d1ee16ec5356c6f24b031bb
Change-Id: Ie5307769e5e3913de4b974d8f3d829cacc84aa9e
Signed-off-by: Sebastian Ene <sebastianene@google.com>
Reported-by: Arve Hjønnevåg <arve@android.com>