iio: adc: ti-ads131e08: return correct error code

The error code returned from devm_iio_trigger_register() inturn
iio_trigger_register() can be other than -ENOMEM. Hence return the
same value as it was returned from the function call.
This change makes devm_iio_trigger_register() handling uniform with
other iio drivers.

Signed-off-by: Dixit Parmar <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/ti-ads131e08.c

···
 	ret = devm_iio_trigger_register(&spi->dev, st->trig);
 	if (ret) {
 		dev_err(&spi->dev, "failed to register IIO trigger\n");
-		return -ENOMEM;
+		return ret;
 	}
 
 	indio_dev->trig = iio_trigger_get(st->trig);