iio: adc: stm32-adc: improve calibration error log

Add more information in calibration error log to differentiate
single-ended and differential calibration.
Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Reviewed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20221115103124.70074-3-olivier.moysan@foss.st.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/stm32-adc.c

@@ -1109,7 +1109,7 @@ static int stm32h7_adc_selfcalib(struct iio_dev *indio_dev, int do_lincal)
 					   !(val & STM32H7_ADCAL), 100,
 					   STM32H7_ADC_CALIB_TIMEOUT_US);
 	if (ret) {
-		dev_err(&indio_dev->dev, "calibration failed\n");
+		dev_err(&indio_dev->dev, "calibration (single-ended) error %d\n", ret);
 		goto out;
 	}
 
@@ -1125,7 +1125,8 @@ static int stm32h7_adc_selfcalib(struct iio_dev *indio_dev, int do_lincal)
 					   !(val & STM32H7_ADCAL), 100,
 					   STM32H7_ADC_CALIB_TIMEOUT_US);
 	if (ret) {
-		dev_err(&indio_dev->dev, "calibration failed\n");
+		dev_err(&indio_dev->dev, "calibration (diff%s) error %d\n",
+			(msk & STM32H7_ADCALLIN) ? "+linear" : "", ret);
 		goto out;
 	}