iio: chemical: bme680: Fix calibration data variable

According to the BME68x Sensor API [1], the h6 calibration
data variable should be an unsigned integer of size 8.

[1]: https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/bme68x_defs.h#L789

Fixes: 1b3bd859 ("iio: chemical: Add support for Bosch BME680 sensor")
Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
Link: https://lore.kernel.org/r/20240606212313.207550-3-vassilisamir@gmail.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/chemical/bme680_core.c

@@ -38,7 +38,7 @@ struct bme680_calib {
 	s8  par_h3;
 	s8  par_h4;
 	s8  par_h5;
-	s8  par_h6;
+	u8  par_h6;
 	s8  par_h7;
 	s8  par_gh1;
 	s16 par_gh2;