libhardware: add data field for proximity sensors

Signed-off-by: Iliyan Malchev <malchev@google.com>
diff --git a/include/hardware/sensors.h b/include/hardware/sensors.h
index a6bee56..a8e538d 100644
--- a/include/hardware/sensors.h
+++ b/include/hardware/sensors.h
@@ -216,6 +216,9 @@
 
         /* temperature is in degrees centigrade (Celsius) */
         float           temperature;
+
+        /* distance in centimeters */
+        float           distance;
     };
 
     /* time is in nanosecond */