f2fs: add SPDX license identifiers

Remove the verbose license text from f2fs files and replace them with
SPDX tags.  This does not change the license of any of the code.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/trace.h b/fs/f2fs/trace.h
index 67db24a..e8075fc 100644
--- a/fs/f2fs/trace.h
+++ b/fs/f2fs/trace.h
@@ -1,12 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * f2fs IO tracer
  *
  * Copyright (c) 2014 Motorola Mobility
  * Copyright (c) 2014 Jaegeuk Kim <jaegeuk@kernel.org>
- *
- * 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.
  */
 #ifndef __F2FS_TRACE_H__
 #define __F2FS_TRACE_H__