crypto: ccree - adjust hash length to suit certain context specifics

Adjust hash length such that it will not be fixed and general for all algs.
Instead make it suitable for certain context information.
This is preparation for SM3 support.

Signed-off-by: Yael Chemla <yael.chemla@foss.arm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>