iio: adc128s052: use SPDX-License-Identifier

This updates the ti-adc128s052.c file to use SPDX-License-Identifier
instead of more verbose license text.
Signed-off-by: Dan O'Donovan <dan@emutex.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ti-adc128s052.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2014 Angelo Compagnucci <angelo.compagnucci@gmail.com>
  *
@@ -6,10 +7,6 @@
  * http://www.ti.com/lit/ds/symlink/adc128s052.pdf
  * http://www.ti.com/lit/ds/symlink/adc122s021.pdf
  * http://www.ti.com/lit/ds/symlink/adc124s021.pdf
- *
- * 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/acpi.h>