mfd: madera: Fixup SPDX headers

GPL-2.0-only is the preferred way of expressing v2 of the GPL, so switch
to that. Remove some redundant copyright notices and correct some
instances where the wrong comment type has been used in header files.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/cs47l90-tables.c b/drivers/mfd/cs47l90-tables.c
index 2c761fc..7345fc0 100644
--- a/drivers/mfd/cs47l90-tables.c
+++ b/drivers/mfd/cs47l90-tables.c
@@ -1,12 +1,8 @@
-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Regmap tables for CS47L90 codec
  *
  * Copyright (C) 2015-2017 Cirrus Logic
- *
- * 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; version 2.
  */
 
 #include <linux/device.h>