[LIS2MDL] Driver for the LIS2MDL magnetometer

SPI driver, prints out sensor temperature and magnetic field in x, y, z coordinates.

src/tests/sensors/test-lis2mdl.cpp

@@ -38,6 +38,7 @@ int main()
 
     clk.mode(Mode::ALTERNATE);
     clk.alternateFunction(5);
+    clk.speed(Speed::_100MHz);
 
     miso.mode(Mode::ALTERNATE);
     miso.alternateFunction(5);