KVM: arm64: Add PROTECTED_NVHE_STACKTRACE Kconfig

This can be used to disable stacktrace for the protected KVM
nVHE hypervisor, in order to save on the associated memory usage.

This option is disabled by default, since protected KVM is not widely
used on platforms other than Android currently.

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220726073750.3219117-13-kaleshsingh@google.com