staging: iio: ade7854-spi: Fix return value

ade7854_probe can fail. Return the value obtained from it
instead of 0 (success).

Signed-off-by: Sachin Kamat <[e-mail]>
Cc: Barry Song <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/staging/iio/meter/ade7854-spi.c

···
 	if (ret)
 		iio_device_free(indio_dev);
 
-	return 0;
+	return ret;
 }
 
 static int ade7854_spi_remove(struct spi_device *spi)