crypto: sahara - avoid needlessly saving and restoring sahara_ctx

Based on commit 434b4212 ("crypto: caam - avoid needlessly saving and
restoring caam_hash_ctx") from Russell King.

When exporting and importing the hash state, we will only export and
import into hashes which share the same struct crypto_ahash pointer.
(See hash_accept->af_alg_accept->hash_accept_parent.)

This means that saving the sahara_ctx structure on export, and
restoring it on import is a waste of resources.  So, remove this code.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>