crypto: crypto4xx - fix an error code

If 'kzalloc' fails, we return 0 which means success.
return -ENOMEM instead as already done a few lines above.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>