iio: adc: rcar-gyroadc: convert to SPDX identifiers

This patch updates license to use SPDX-License-Identifier
instead of verbose license text.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/rcar-gyroadc.c

+// SPDX-License-Identifier: GPL-2.0+
 /*
  * Renesas R-Car GyroADC driver
  *
  * Copyright 2016 Marek Vasut <marek.vasut@gmail.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.
  */
 
 #include <linux/module.h>