crypto: sha256 - Optimized sha256 x86_64 routine using AVX2's RORX instructions

Provides SHA256 x86_64 assembly routine optimized with SSE, AVX and
AVX2's RORX instructions.  Speedup of 70% or more has been
measured over the generic implementation.

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>