iio: adc: ad7124: set initial ADC mode to idle

During setup the st->adc_control is 0, which corresponds to a continuous
conversion mode. The reset value for channel 1 is to enable it. The
combined effect of these two is that the ADC will start conversions for
channel 1 without them being read.
This is not neccessarily a problem, but it is an unexpected behavior.

Set the ADC state to idle during setup to avoid this.
Signed-off-by: Dumitru Ceclan <dumitru.ceclan@analog.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240731-ad7124-fix-v1-4-46a76aa4b9be@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7124.c

@@ -896,6 +896,9 @@ static int ad7124_setup(struct ad7124_state *st)
 	st->adc_control &= ~AD7124_ADC_CTRL_PWR_MSK;
 	st->adc_control |= AD7124_ADC_CTRL_PWR(power_mode);
 
+	st->adc_control &= ~AD7124_ADC_CTRL_MODE_MSK;
+	st->adc_control |= AD7124_ADC_CTRL_MODE(AD_SD_MODE_IDLE);
+
 	mutex_init(&st->cfgs_lock);
 	INIT_KFIFO(st->live_cfgs_fifo);
 	for (i = 0; i < st->num_channels; i++) {