iio: chemical: scd4x: Add pressure compensation

This patch adds pressure compensation to the scd4x driver. The pressure can
be written to the sensor in hPa. The pressure will be compensated
internally by the sensor.

Signed-off-by: Roan van Dijk <roan@protonic.nl>
Link: https://lore.kernel.org/r/20230711101419.2065107-1-roan@protonic.nl
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>