iio: adc: max11100: 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/max11100.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * iio/adc/max11100.c
  * Maxim max11100 ADC Driver with IIO interface
  *
  * Copyright (C) 2016-17 Renesas Electronics Corporation
  * Copyright (C) 2016-17 Jacopo Mondi
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
  */
 #include <linux/delay.h>
 #include <linux/kernel.h>