nand_util.c: Correct licensing

Prior to SPDX licensing this file was GPL-2.0 with Freescale granting
rights for "or later" for their contributed code.  We incorrectly moved
this file to GPL-2.0+, so correct it to GPL-2.0.  In addition we cannot
easily denote in the file where or what code is "or later", so just set
that aside for now and the file as a whole is GPL-2.0 regardless.

Cc: Scott Wood <scottwood@freescale.com>
Signed-off-by: Tom Rini <trini@ti.com>

drivers/mtd/nand/nand_util.c

@@ -14,7 +14,9 @@
  * Copyright (C) 2008 Nokia Corporation: drop_ffs() function by
  * Artem Bityutskiy <dedekind1@gmail.com> from mtd-utils
  *
- * SPDX-License-Identifier:	GPL-2.0+
+ * Copyright 2010 Freescale Semiconductor
+ *
+ * SPDX-License-Identifier:	GPL-2.0
  */
 
 #include <common.h>