sensor: add helper function for convert radians and 10 micro degrees

This helper function would be used by Sensor SubSystem(senss).

When the unit is 1 micro degree, the range that the int32_t can
represent is +/-2147.483 degrees. In order to increase this range,
here we use 10 micro degrees as the unit.

Signed-off-by: Zhang Lixu <lixu.zhang@intel.com>