firmware-utils: osbridge-crc: replace GPL-2.0-only boilerplate with SPDX

This was missed because scancode license scanner was confused by
comments about crc32buf().

Cc: Gabor Juhos <[email protected]>
Cc: Gabor Juhos <[email protected]>
Signed-off-by: Rafał Miłecki <[email protected]>

tools/firmware-utils/src/osbridge-crc.c

@@ -1,10 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  Copyright (C) 2009 Gabor Juhos <[email protected]>
- *
- *  This program is free software; you can redistribute it and/or modify it
- *  under the terms of the GNU General Public License version 2 as published
- *  by the Free Software Foundation.
- *
  */
 
 #include <stdio.h>