hwc: Fix klockwork errors

Resolving klockwork errors to avoid memory leaks,
improper assignments in liboverlay.

Change-Id: I82ac6ae782c7b783e89999b832bbd1d361376b9f
diff --git a/libgralloc/alloc_controller.h b/libgralloc/alloc_controller.h
index 5fe81fa..f0b8ed9 100644
--- a/libgralloc/alloc_controller.h
+++ b/libgralloc/alloc_controller.h
@@ -65,6 +65,7 @@
 
     private:
     IonAlloc* mIonAlloc;
+    void allocateIonMem();
 
 };
 } //end namespace gralloc