spi: mxs: Switch to SPDX identifier

Adopt the SPDX license identifier headers to ease license compliance
management.

Cc: Marek Vasut <marex@denx.de>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-mxs.c

-/*
- * Freescale MXS SPI master driver
- *
- * Copyright 2012 DENX Software Engineering, GmbH.
- * Copyright 2012 Freescale Semiconductor, Inc.
- * Copyright 2008 Embedded Alley Solutions, Inc All Rights Reserved.
- *
- * Rework and transition to new API by:
- * Marek Vasut <marex@denx.de>
- *
- * Based on previous attempt by:
- * Fabio Estevam <fabio.estevam@freescale.com>
- *
- * Based on code from U-Boot bootloader by:
- * Marek Vasut <marex@denx.de>
- *
- * Based on spi-stmp.c, which is:
- * Author: Dmitry Pervushin <dimka@embeddedalley.com>
- *
- * 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.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- */
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Freescale MXS SPI master driver
+//
+// Copyright 2012 DENX Software Engineering, GmbH.
+// Copyright 2012 Freescale Semiconductor, Inc.
+// Copyright 2008 Embedded Alley Solutions, Inc All Rights Reserved.
+//
+// Rework and transition to new API by:
+// Marek Vasut <marex@denx.de>
+//
+// Based on previous attempt by:
+// Fabio Estevam <fabio.estevam@freescale.com>
+//
+// Based on code from U-Boot bootloader by:
+// Marek Vasut <marex@denx.de>
+//
+// Based on spi-stmp.c, which is:
+// Author: Dmitry Pervushin <dimka@embeddedalley.com>
 
 #include <linux/kernel.h>
 #include <linux/ioport.h>