KVM: arm64: Add PKVM_DISABLE_STAGE2_ON_PANIC

KVM: arm64: Add PKVM_DISABLE_STAGE2_ON_PANIC

On NVHE_EL2_DEBUG, when using pKVM, the host stage-2 is relaxed to grant
the kernel access to the stacktrace, hypervisor bug table and text to
symbolize addresses. This is unsafe for production. In preparation for
adding more debug options to NVHE_EL2_DEBUG, decouple the stage-2
relaxation into a separate option.

While at it, rename PROTECTED_NVHE_STACKTRACE into PKVM_STACKTRACE,
following the same naming scheme as PKVM_DISABLE_STAGE2_ON_PANIC.

Reviewed-by: Kalesh Singh <kaleshsingh@google.com>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Link: https://patch.msgid.link/20260309162516.2623589-20-vdonnefort@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>