cert_create: update help message

The help message printed by the cert_create tool using the command
line option -h (or --help) does not correctly list all the available
command line options.

This patch reworks the print_help() function to print the help
messages in a data driven approach. For each command line option
registered, an optional help message can be specified, which will
be printed by print_help().

Help messages for the TBBR options (certificates, keys and images)
are also provided.

Fix a small bug in the short options string passed to getopt_long:
the ':' was missing in the '-a' option (this option must take an
argument).

Fixes ARM-software/tf-issues#337

Change-Id: I9d08c2dfd349022808fcc884724f677eefdc1452
diff --git a/tools/cert_create/src/cmd_opt.c b/tools/cert_create/src/cmd_opt.c
index 3847b98..ecf84ab 100644
--- a/tools/cert_create/src/cmd_opt.c
+++ b/tools/cert_create/src/cmd_opt.c
@@ -28,26 +28,35 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <assert.h>
 #include <getopt.h>
 #include <stddef.h>
+#include <stdlib.h>
 #include <cmd_opt.h>
+#include "debug.h"
 
 /* Command line options */
 static struct option long_opt[CMD_OPT_MAX_NUM+1];
+static const char *help_msg[CMD_OPT_MAX_NUM+1];
 static int num_reg_opt;
 
-int cmd_opt_add(const char *name, int has_arg, int val)
+void cmd_opt_add(const cmd_opt_t *cmd_opt)
 {
+	assert(cmd_opt != NULL);
+
 	if (num_reg_opt >= CMD_OPT_MAX_NUM) {
-		return -1;
+		ERROR("Out of memory. Please increase CMD_OPT_MAX_NUM\n");
+		exit(1);
 	}
-	long_opt[num_reg_opt].name = name;
-	long_opt[num_reg_opt].has_arg = has_arg;
+
+	long_opt[num_reg_opt].name = cmd_opt->long_opt.name;
+	long_opt[num_reg_opt].has_arg = cmd_opt->long_opt.has_arg;
 	long_opt[num_reg_opt].flag = 0;
-	long_opt[num_reg_opt].val = val;
-	num_reg_opt++;
+	long_opt[num_reg_opt].val = cmd_opt->long_opt.val;
 
-	return 0;
+	help_msg[num_reg_opt] = cmd_opt->help_msg;
+
+	num_reg_opt++;
 }
 
 const struct option *cmd_opt_get_array(void)
@@ -63,3 +72,12 @@
 
 	return long_opt[idx].name;
 }
+
+const char *cmd_opt_get_help_msg(int idx)
+{
+	if (idx >= num_reg_opt) {
+		return NULL;
+	}
+
+	return help_msg[idx];
+}