crypto: sha256-mb - Algorithm data structures

This patch introduces the data structures and prototypes of
functions needed for computing SHA256 hash using multi-buffer.
Included are the structures of the multi-buffer SHA256 job,
job scheduler in C and x86 assembly.

Signed-off-by: Megha Dey <megha.dey@linux.intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>