EVP_Digest*Update, EVP_DigestFinal, and HMAC_Update can never fail.

Enough code fails to check their return codes anyway. We ought to make
it official.

Change-Id: Ie646360fd7073ea943036f5e21bed13df7e1b77a
Reviewed-on: https://boringssl-review.googlesource.com/4954
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/hmac.h b/include/openssl/hmac.h
index 89cdf8f..b8cf4af 100644
--- a/include/openssl/hmac.h
+++ b/include/openssl/hmac.h
@@ -106,7 +106,7 @@
                                 const EVP_MD *md, ENGINE *impl);
 
 /* HMAC_Update hashes |data_len| bytes from |data| into the current HMAC
- * operation in |ctx|. It returns one on success and zero on error. */
+ * operation in |ctx|. It returns one. */
 OPENSSL_EXPORT int HMAC_Update(HMAC_CTX *ctx, const uint8_t *data,
                                size_t data_len);