ANDROID: KVM: arm64: pkvm: Ensure that TLBs and I-cache are private to each vcpu

If a different vcpu from the same vm is loaded on the same
physical CPU, we must flush the CPU context.

This patch ensures that by tracking the vcpu that was last loaded
on this CPU, and flushes if that changes. This could lead to
over-invalidation, which could affect performance but not
correctness.

Bug: 228810735
Signed-off-by: Fuad Tabba <tabba@google.com>
Change-Id: Ic623d98bfe3156591640f6b7908fb836456c2bd0