Add KEYCODE_SOFT_SLEEP for Ungaze.

BUG: b/23589870
Change-Id: I9bb575fe97bfae926ef4db37615e88057b81480c
diff --git a/include/input/InputEventLabels.h b/include/input/InputEventLabels.h
index 344f2f3..f0a6238 100644
--- a/include/input/InputEventLabels.h
+++ b/include/input/InputEventLabels.h
@@ -311,6 +311,7 @@
     DEFINE_KEYCODE(MEDIA_SKIP_BACKWARD),
     DEFINE_KEYCODE(MEDIA_STEP_FORWARD),
     DEFINE_KEYCODE(MEDIA_STEP_BACKWARD),
+    DEFINE_KEYCODE(SOFT_SLEEP),
 
     { NULL, 0 }
 };