crypto: x86 - Rename functions to avoid conflict with crypto/sha256.h

Rename static / file-local functions so that they do not conflict with
the functions declared in crypto/sha256.h.

This is a preparation patch for folding crypto/sha256.h into crypto/sha.h.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>