pinctrl: 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: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/cirrus/pinctrl-cs47l35.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Pinctrl for Cirrus Logic CS47L35
  *
  * Copyright (C) 2016-2017 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/err.h>

drivers/pinctrl/cirrus/pinctrl-cs47l85.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Pinctrl for Cirrus Logic CS47L85
  *
  * Copyright (C) 2016-2017 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/err.h>

drivers/pinctrl/cirrus/pinctrl-cs47l90.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Pinctrl for Cirrus Logic CS47L90
  *
  * Copyright (C) 2016-2017 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/err.h>

drivers/pinctrl/cirrus/pinctrl-madera-core.c

-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Pinctrl for Cirrus Logic Madera codecs
  *
  * Copyright (C) 2016-2018 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/err.h>

drivers/pinctrl/cirrus/pinctrl-madera.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * Pinctrl for Cirrus Logic Madera codecs
  *
  * Copyright (C) 2016-2017 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.
  */
 
 #ifndef PINCTRL_MADERA_H