KVM: arm64: pkvm: Implement CONFIG_DEBUG_LIST at EL2

Currently the check functions are stubbed out at EL2. Implement
versions suitable for the constrained EL2 environment.

Signed-off-by: Keir Fraser <keirf@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220131124114.3103337-1-keirf@google.com