crypto: sha512 - Expose generic sha512 routine to be callable from ot… …her modules 1

Other SHA512 routines may need to use the generic routine when
FPU is not available.

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>

https://github.com/neobuddy89/hammerhead/commit/b08b53f9e45ee65403b703fb7c7fb497da0ef7c3