Heroc: Report 0 instead of max lux on wrong read

Borrowed from Bravo/Bravoc.

Change-Id: Ic7471cd3e44657ed202ace1d5b8556505dafd8a5

libsensors/LightSensor.cpp

@@ -157,6 +157,6 @@ float LightSensor::indexToValue(size_t index) const
 
     const size_t maxIndex = sizeof(luxValues)/sizeof(*luxValues) - 1;
     if (index > maxIndex)
-        index = maxIndex;
+        index = 0;
     return luxValues[index];
 }