ANDROID: KVM: arm64: Handle hyp s1 allocation failures gracefully

Now that we have removed several indirection layers in the mem_protect
machinery, it becomes a little simpler to handle allocation failures
gracefully. Use this opportunity to handle hyp stage-1 mapping failures
without BUG-ing, hence paving the way for reducing its associated
carveout.

[@vdonnefort: Rework for the pre-6.12 mem_protect machinery]

Bug: 273700914
Bug: 239674049
Suggested-by: Vincent Donnefort <vdonnefort@google.com>
Change-Id: Ib8b27e59903f3223eaf82a915fe45ba4bcf976ba
Signed-off-by: Quentin Perret <qperret@google.com>