openocd: src: replace SPDX to remaining files

With most of the files already processed through scripts, replace
manually the license to the few remaining files.

Change-Id: I3c7131e66b89ddad482f1074b5be5a9a69fdf6fd
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7073
Tested-by: jenkins

src/helper/update_jep106.pl

@@ -1,4 +1,6 @@
 #!/usr/bin/perl
+# SPDX-License-Identifier: GPL-2.0-or-later
+
 use strict;
 use warnings;
 use File::Basename;