KVM: arm64: selftests: Convert to kernel's ESR terminology

Drop the KVM selftests specific flavoring of ESR in favor of the kernel
header.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20241025203106.3529261-4-oliver.upton@linux.dev


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>