iio: adc: meson-saradc: do not use meson_sar_adc_iio_channels directly

In the future we may support two different channel sets:
- one which includes the voltage pads and the temperature sensor output
  (for Meson8, Meson8b and Meson8m2)
- one which only includes the voltage pads (GXBB, GXL, GXM and AXG)

Channel 7 has a special function on all of these platforms. However,
since we will have different channel array definitions we want our code
to always use whatever channels struct iio_dev uses.

No functional changes for now. This is the preparation for adding
temperature sensor support to this driver.
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/meson_saradc.c

@@ -854,7 +854,7 @@ static int meson_sar_adc_calib(struct iio_dev *indio_dev)
 	meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_DIV4);
 	usleep_range(10, 20);
 	ret = meson_sar_adc_get_sample(indio_dev,
-				       &meson_sar_adc_iio_channels[7],
+				       &indio_dev->channels[7],
 				       MEAN_AVERAGING, EIGHT_SAMPLES, &value0);
 	if (ret < 0)
 		goto out;
@@ -862,7 +862,7 @@ static int meson_sar_adc_calib(struct iio_dev *indio_dev)
 	meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_MUL3_DIV4);
 	usleep_range(10, 20);
 	ret = meson_sar_adc_get_sample(indio_dev,
-				       &meson_sar_adc_iio_channels[7],
+				       &indio_dev->channels[7],
 				       MEAN_AVERAGING, EIGHT_SAMPLES, &value1);
 	if (ret < 0)
 		goto out;