cifs: cifs_md4 convert to SPDX identifier

Add SPDX license identifier and replace license boilerplate
for cifs_md4.c
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2maperror.c

 // SPDX-License-Identifier: LGPL-2.1
 /*
- *   fs/smb2/smb2maperror.c
  *
  *   Functions which do error mapping of SMB2 status codes to POSIX errors
  *

fs/cifs_common/cifs_md4.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Cryptographic API.
  *
@@ -14,11 +15,6 @@
  * Copyright (c) 2002 David S. Miller (davem@redhat.com)
  * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
  *
- * 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 2 of the License, or
- * (at your option) any later version.
- *
  */
 #include <linux/init.h>
 #include <linux/kernel.h>