contrib: replace the GPLv3-or-later license tag

These files are not built in OpenOCD and are not in conflict with
OpenOCD license.

Replace the GPL boilerplate with the SPDX tag.
Add the SPDX tag.

The SPDX tag on files *.c is incorrect, as it should use the C99
single line comment using '//'. But current checkpatch doesn't
allow C99 comments, so keep using standard C comments, by now.

Change-Id: I934e4add24098f0e8574120b3bc32e9bcf166abd
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7157
Tested-by: jenkins

contrib/itmdump.c

@@ -1,19 +1,6 @@
-/*
- * Copyright (C) 2010 by David Brownell
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or (at
- * your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+
+/* Copyright (C) 2010 by David Brownell */
 
 /*
  * Simple utility to parse and dump ARM Cortex-M3 SWO trace output.  Once the

contrib/rpc_examples/ocd_rpc_example.py

@@ -1,4 +1,6 @@
 #!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-3.0-or-later
+
 """
 OpenOCD RPC example, covered by GNU GPLv3 or later
 Copyright (C) 2014 Andreas Ortmann (ortmann@finf.uni-hannover.de)

contrib/rpc_examples/ocdrpc.hs

@@ -1,4 +1,6 @@
--- OpenOCD RPC example, covered by GNU GPLv3 or later
+-- SPDX-License-Identifier: GPL-3.0-or-later
+
+-- OpenOCD RPC example
 -- Copyright (C) 2014 Paul Fertser
 --
 -- Example output: