Currently the check functions are stubbed out at EL2. Implement
versions suitable for the constrained EL2 environment.
Signed-off-by: NKeir Fraser <keirf@google.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220131124114.3103337-1-keirf@google.com