crypto: omap-des - fix error return code in omap_des_probe()

Fix to return error code -ENOMEM from the crypto_engine_alloc_init()
error handling case instead of 0, as done elsewhere in this function.

Fixes: f1b77aac ("crypto: omap-des - Integrate with the crypto
engine framework")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>