iio: humidity: hdc100x: fix IIO_TEMP channel reporting

IIO_TEMP channel was being incorrectly reported back as Celsius when it
should have been milliCelsius. This is via an incorrect scale value being
returned to userspace.

Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>