set vsync power hint

Change-Id: I28c2faf9ff584df3e74392712971cbcf75eb9e98
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index 76aadf8..aada3cd 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -86,7 +86,7 @@
         EVENT_VSYNC = HWC_EVENT_VSYNC
     };
 
-    status_t eventControl(int event, int enabled);
+    void eventControl(int event, int enabled);
 
     // this class is only used to fake the VSync event on systems that don't
     // have it.