[LIS2MDL] Fixed scale and two's complement conversion

CMakeLists.txt

src/shared/sensors/BMX160/BMX160Defs.h

src/shared/sensors/LIS2MDL/LIS2MDL.cpp

src/shared/sensors/LIS2MDL/LIS2MDL.h

src/shared/sensors/LIS3MDL/LIS3MDL.cpp

src/shared/sensors/LIS3MDL/LIS3MDL.h

src/tests/sensors/test-lis2mdl.cpp