iio: chemical: bme680: Fix pressure value output

The IIO standard units are measured in kPa while the driver
is using hPa.

Apart from checking the userspace value itself, it is mentioned also
in the Bosch API [1] that the pressure value is in Pascal.

[1]: https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/bme68x_defs.h#L742

Fixes: 1b3bd859

 ("iio: chemical: Add support for Bosch BME680 sensor")
Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
Link: https://lore.kernel.org/r/20240606212313.207550-2-vassilisamir@gmail.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>