kernel: cgroup: Add LGPL-2.1 SPDX license ID to legacy_freezer.c

Add an appropriate SPDX-License-Identifier line to the file,
and remove the GNU boilerplate text.

Signed-off-by: Tim Bird <tim.bird@sony.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Author: tbird20d

kernel/cgroup/legacy_freezer.c

@@ -1,17 +1,10 @@
+// SPDX-License-Identifier: LGPL-2.1
 /*
  * cgroup_freezer.c -  control group freezer subsystem
  *
  * Copyright IBM Corporation, 2007
  *
  * Author : Cedric Le Goater <clg@fr.ibm.com>
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of version 2.1 of the GNU Lesser General Public License
- * as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it would be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  */
 
 #include <linux/export.h>