iio: accel: adxl380: fix raw sample read

The adxl380_read_chn function returns either a negative value in case an
error occurs or the actual sample.

Check only for negative values after a channel is read.

Link: https://lore.kernel.org/lkml/20241101095202.20121-1-antoniu.miclaus@analog.com/
Fixes: 90a7580 ("iio: accel: add ADXL380 driver")
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>

Author: amiclaus

drivers/iio/accel/adxl380.c

@@ -1181,7 +1181,7 @@ static int adxl380_read_raw(struct iio_dev *indio_dev,
 			return ret;
 
 		ret = adxl380_read_chn(st, chan->address);
-		if (ret)
+		if (ret < 0)
 			return ret;
 
 		iio_device_release_direct_mode(indio_dev);