crypto: caam - refactor ahash_edesc_alloc

Changed parameters for ahash_edesc_alloc function:
- remove flags since they can be computed in
ahash_edesc_alloc, the only place they are needed;
- use ahash_request instead of caam_hash_ctx, to be
able to compute gfp flags.

Signed-off-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Reviewed-by: Horia Geanta <horia.geanta@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>