iio: stm32: Adopt SPDX identifier

Add SPDX identifier in stm32's files in IIO directory

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Acked-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Acked-by: Philippe Ombredanne <pombredanne@nexb.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/iio/adc/stm32-adc-core.c b/drivers/iio/adc/stm32-adc-core.c
index 6aefef9..40be7d9 100644
--- a/drivers/iio/adc/stm32-adc-core.c
+++ b/drivers/iio/adc/stm32-adc-core.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * This file is part of STM32 ADC driver
  *
@@ -6,19 +7,6 @@
  *
  * Inspired from: fsl-imx25-tsadc
  *
- * License type: GPLv2
- *
- * 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.
- *
- * 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.
- *
- * You should have received a copy of the GNU General Public License along with
- * this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <linux/clk.h>