crypto: sha256 - Expose SHA256 generic routine to be callable externally.

Other SHA256 routine 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>

include/crypto/sha.h

@@ -87,4 +87,6 @@ struct shash_desc;
 extern int crypto_sha1_update(struct shash_desc *desc, const u8 *data,
 			      unsigned int len);
 
+extern int crypto_sha256_update(struct shash_desc *desc, const u8 *data,
+			      unsigned int len);
 #endif