iio: adc: ad_sigma_delta: Disable channel after calibration

iio: adc: ad_sigma_delta: Disable channel after calibration

The function ad_sd_calibrate() enables the channel to calibrate at
function entry but doesn't disable it on exit. This is problematic
because if two (or more) channels are calibrated in a row, the second
calibration isn't executed as intended as the first (still enabled)
channel is recalibrated and after the first irq (i.e. when the
calibration of the first channel completed) the calibration is aborted.

This currently affects ad7173 only, as the other drivers using
ad_sd_calibrate() never have more than one channel enabled at a time.

To fix this, disable the calibrated channel after calibration.

Fixes: 031bdc8aee01 ("iio: adc: ad7173: add calibration support")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://patch.msgid.link/20250303114659.1672695-11-u.kleine-koenig@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>