crypto: n2/des - fix build breakage after DES updates

Fix build breakage caused by the DES library refactor.

Fixes: d4b90dbc ("crypto: n2/des - switch to new verification routines")
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>