iio: dac/ad5755: signedness bug in ad5755_setup_pdata()

We need "ret" to be signed for the error handling to work correctly.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/dac/ad5755.c b/drivers/iio/dac/ad5755.c
index e6dbe5f..5db3506 100644
--- a/drivers/iio/dac/ad5755.c
+++ b/drivers/iio/dac/ad5755.c
@@ -451,9 +451,9 @@
 	const struct ad5755_platform_data *pdata)
 {
 	struct ad5755_state *st = iio_priv(indio_dev);
-	unsigned int ret;
 	unsigned int val;
 	unsigned int i;
+	int ret;
 
 	if (pdata->dc_dc_phase > AD5755_DC_DC_PHASE_90_DEGREE ||
 		pdata->dc_dc_freq > AD5755_DC_DC_FREQ_650kHZ ||