iio: dac: ti-dac5571: fix an error code in probe()

If we have an unexpected number of channels then return -EINVAL instead
of returning success.

Fixes: df38a4a7 ("iio: dac: add TI DAC5571 family support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20210816183954.GB2068@kiliSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dac/ti-dac5571.c

@@ -350,6 +350,7 @@ static int dac5571_probe(struct i2c_client *client,
 		data->dac5571_pwrdwn = dac5571_pwrdwn_quad;
 		break;
 	default:
+		ret = -EINVAL;
 		goto err;
 	}