dt-bindings: iio/adc: Add bindings for Ingenic JZ47xx SoCs ADC.

Add device tree bindings for the ADC controller on JZ47xx SoCs,
used by the ingenic-adc driver.
Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

include/dt-bindings/iio/adc/ingenic,adc.h

+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _DT_BINDINGS_IIO_ADC_INGENIC_ADC_H
+#define _DT_BINDINGS_IIO_ADC_INGENIC_ADC_H
+
+/* ADC channel idx. */
+#define INGENIC_ADC_AUX		0
+#define INGENIC_ADC_BATTERY	1
+
+#endif