EC_GROUP_cmp should return zero if the groups match.

(I got this wrong when reading the OpenSSL code.)

Change-Id: Ib289ef41d0ab5a3157ad8b9454d2de96d1f86c22
Reviewed-on: https://boringssl-review.googlesource.com/3620
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/ec.h b/include/openssl/ec.h
index c952d9a..318ce0f 100644
--- a/include/openssl/ec.h
+++ b/include/openssl/ec.h
@@ -115,7 +115,7 @@
  * error. */
 OPENSSL_EXPORT EC_GROUP *EC_GROUP_dup(const EC_GROUP *a);
 
-/* EC_GROUP_cmp returns one if |a| and |b| are the same group and zero
+/* EC_GROUP_cmp returns zero if |a| and |b| are the same group and non-zero
  * otherwise. */
 OPENSSL_EXPORT int EC_GROUP_cmp(const EC_GROUP *a, const EC_GROUP *b,
                                 BN_CTX *ignored);