Code cleaning in BMA421 driver. Do the axis inversion in the driver and not in the application.

NOTE: Axis remapping from the SDK do not apply to the "raw" X/Y/Z values returned to the sensor. According to the doc, the remapping is only applied to features, but I cannot check if it has any effect on step counting (I'm not sure I use it correctly, doc is not complete enough about this feature).

src/systemtask/SystemTask.cpp

@@ -243,8 +243,8 @@ void SystemTask::UpdateMotion() {
   if(isSleeping)
     twiMaster.Sleep();
 
-  motionController.Update(motionValues.y,
-                          motionValues.x,
+  motionController.Update(motionValues.x,
+                          motionValues.y,
                           motionValues.z,
                           motionValues.steps);
   if (motionController.ShouldWakeUp(isSleeping)) {