iio: adc: mcp3564: replace sprintf() with sysfs_emit()

Update the mcp3564_read_label() function to use sysfs_emit() for
generating labels.

Signed-off-by: Nuno Sá <[e-mail]>
Reviewed-by: Marius Cristea <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/mcp3564.c

···
 {
 	struct mcp3564_state *adc = iio_priv(indio_dev);
 
-	return sprintf(label, "%s\n", adc->labels[chan->scan_index]);
+	return sysfs_emit(label, "%s\n", adc->labels[chan->scan_index]);
 }
 
 static int mcp3564_parse_fw_children(struct iio_dev *indio_dev)