iio: adc: ad_sigma_delta: Add error checking for ad_sigma_delta_set_channel()

All other calls to ad_sigma_delta_set_channel() in ad_sigma_delta.c
check the return value afterwards. Do it for all calls.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://patch.msgid.link/20250303114659.1672695-16-u.kleine-koenig@baylibre.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>