IIO trigger handlers must call iio_trigger_notify_done() when done. This
must be done even when an error occurred. Otherwise the trigger will be
seen as busy indefinitely and the trigger handler will never be called
again.

The ad7768-1 driver neglects to call iio_trigger_notify_done() when there
is an error reading the converter data. Fix this by making sure that
iio_trigger_notify_done() is included in the error exit path.

Fixes: a5f8c7da ("iio: adc: Add AD7768-1 ADC basic support")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20211101144055.13858-2-lars@metafoo.de
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>