staging: exfat - fix SPDX tags..

The copyright notices as I got them said "GPLv2 or later", which I
screwed up when putting in the SPDX tags.  Fix them to match the
license I got the code under.
Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>

Link: https://lore.kernel.org/r/122590.1568853488@turing-policeSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/exfat/Makefile

-# SPDX-License-Identifier: GPL-2.0
+# SPDX-License-Identifier: GPL-2.0-or-later
 
 obj-$(CONFIG_EXFAT_FS) += exfat.o
 

drivers/staging/exfat/exfat.h

-/* SPDX-License-Identifier: GPL-2.0 */
+/* SPDX-License-Identifier: GPL-2.0-or-later */
 /*
  *  Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
  */

drivers/staging/exfat/exfat_blkdev.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
  */

drivers/staging/exfat/exfat_cache.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
  */

drivers/staging/exfat/exfat_core.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
  */

drivers/staging/exfat/exfat_nls.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
  */

drivers/staging/exfat/exfat_super.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
  */

drivers/staging/exfat/exfat_upcase.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
  */