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/bin2char.sh

@@ -1,4 +1,5 @@
 #!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-or-later
 
 [ $# != 0 ] && {
     echo "Usage: $0"