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: 7c0299e879dd ("iio: adc: Add support for DLN2 ADC")
Signed-off-by: Lars-Peter Clausen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Cc: <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/dln2-adc.c

···
 		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,