iio: adc: meson: add enum for iio channel numbers

Channels could be referenced in the driver code and using enum allows
to make it more robust.
Signed-off-by: George Stark <GNStark@sberdevices.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230714114010.293440-5-gnstark@sberdevices.ruSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/meson_saradc.c

@@ -224,27 +224,39 @@ enum meson_sar_adc_chan7_mux_sel {
 	CHAN7_MUX_CH7_INPUT = 0x7,
 };
 
+enum meson_sar_adc_channel_index {
+	NUM_CHAN_0,
+	NUM_CHAN_1,
+	NUM_CHAN_2,
+	NUM_CHAN_3,
+	NUM_CHAN_4,
+	NUM_CHAN_5,
+	NUM_CHAN_6,
+	NUM_CHAN_7,
+	NUM_CHAN_TEMP,
+};
+
 static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
-	MESON_SAR_ADC_CHAN(0),
-	MESON_SAR_ADC_CHAN(1),
-	MESON_SAR_ADC_CHAN(2),
-	MESON_SAR_ADC_CHAN(3),
-	MESON_SAR_ADC_CHAN(4),
-	MESON_SAR_ADC_CHAN(5),
-	MESON_SAR_ADC_CHAN(6),
-	MESON_SAR_ADC_CHAN(7),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_0),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_1),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_2),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_3),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_4),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_5),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_6),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_7),
 };
 
 static const struct iio_chan_spec meson_sar_adc_and_temp_iio_channels[] = {
-	MESON_SAR_ADC_CHAN(0),
-	MESON_SAR_ADC_CHAN(1),
-	MESON_SAR_ADC_CHAN(2),
-	MESON_SAR_ADC_CHAN(3),
-	MESON_SAR_ADC_CHAN(4),
-	MESON_SAR_ADC_CHAN(5),
-	MESON_SAR_ADC_CHAN(6),
-	MESON_SAR_ADC_CHAN(7),
-	MESON_SAR_ADC_TEMP_CHAN(8),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_0),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_1),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_2),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_3),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_4),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_5),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_6),
+	MESON_SAR_ADC_CHAN(NUM_CHAN_7),
+	MESON_SAR_ADC_TEMP_CHAN(NUM_CHAN_TEMP),
 };
 
 struct meson_sar_adc_param {