iio: dln2: Check return value of devm_iio_trigger_register()

Registering a trigger can fail and the return value of
devm_iio_trigger_register() must be checked. Otherwise undefined behavior
can occur when the trigger is used.

Fixes: 7c0299e879 ("iio: adc: Add support for DLN2 ADC")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20211101133043.6974-1-lars@metafoo.de
Cc: <stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/dln2-adc.c

@@ -655,7 +655,11 @@ static int dln2_adc_probe(struct platform_device *pdev)
 		return -ENOMEM;
 	}
 	iio_trigger_set_drvdata(dln2->trig, dln2);
-	devm_iio_trigger_register(dev, dln2->trig);
+	ret = devm_iio_trigger_register(dev, dln2->trig);
+	if (ret) {
+		dev_err(dev, "failed to register trigger: %d\n", ret);
+		return ret;
+	}
 	iio_trigger_set_immutable(indio_dev, dln2->trig);
 
 	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,