iio: hid-sensor-rotation: Add "scale" and "offset" properties parse support

Add orientation sensor "scale" and "offset" parse support.
These two properties are needed for exponent data conversion.

Signed-off-by: Song Hongyan <hongyan.song@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Xu Even <even.xu@intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>