Add definitions for new head tracker sensor type

Bug: 210156629
Test: n/a
Change-Id: If267401f059fe1377e495a91776b2eb4448fd1ef
diff --git a/include/hardware/sensors-base.h b/include/hardware/sensors-base.h
index ef7eead..b88a8c2 100644
--- a/include/hardware/sensors-base.h
+++ b/include/hardware/sensors-base.h
@@ -52,6 +52,7 @@
     SENSOR_TYPE_LOW_LATENCY_OFFBODY_DETECT = 34,
     SENSOR_TYPE_ACCELEROMETER_UNCALIBRATED = 35,
     SENSOR_TYPE_HINGE_ANGLE = 36,
+    SENSOR_TYPE_HEAD_TRACKER = 37,
     SENSOR_TYPE_DEVICE_PRIVATE_BASE = 65536 /* 0x10000 */,
 };