tools: add an option -hash-alg for cert_create

This option enables the user to select the secure hash algorithm
to be used for generating the hash. It supports the following
options:
    - sha256 (default)
    - sha384
    - sha512

Change-Id: Icb093cec1b5715e248c3d1c3749a2479a7ab4b89
Signed-off-by: Qixiang Xu <qixiang.xu@arm.com>
diff --git a/tools/cert_create/include/cert.h b/tools/cert_create/include/cert.h
index 256e7af..9b4ef5a 100644
--- a/tools/cert_create/include/cert.h
+++ b/tools/cert_create/include/cert.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2017, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -48,7 +48,13 @@
 int cert_init(void);
 cert_t *cert_get_by_opt(const char *opt);
 int cert_add_ext(X509 *issuer, X509 *subject, int nid, char *value);
-int cert_new(int key_alg, cert_t *cert, int days, int ca, STACK_OF(X509_EXTENSION) * sk);
+int cert_new(
+	int key_alg,
+	int md_alg,
+	cert_t *cert,
+	int days,
+	int ca,
+	STACK_OF(X509_EXTENSION) * sk);
 
 /* Macro to register the certificates used in the CoT */
 #define REGISTER_COT(_certs) \