iio: chemical: atlas-ph-sensor: correct IIO_TEMP values to millicelsius

IIO_TEMP scale value for temperature was incorrect and not in millicelsius
as required by the ABI documentation.

Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
Fixes: 27dec00e (iio: chemical: add Atlas pH-SM sensor support)
Cc: <stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>