libhardware: add a field for reporting light levels

Signed-off-by: Iliyan Malchev <malchev@google.com>
diff --git a/include/hardware/sensors.h b/include/hardware/sensors.h
index a8e538d..3be07b3 100644
--- a/include/hardware/sensors.h
+++ b/include/hardware/sensors.h
@@ -219,6 +219,9 @@
 
         /* distance in centimeters */
         float           distance;
+
+	/* light in lux */
+	float           light;
     };
 
     /* time is in nanosecond */