utils: fix warnings for unused parameters

Change-Id: Ibfb755a30ba2923669060fe0aed019beecbe38a1
diff --git a/include/utils/RefBase.h b/include/utils/RefBase.h
index aa91f60..8e304e7 100644
--- a/include/utils/RefBase.h
+++ b/include/utils/RefBase.h
@@ -165,10 +165,10 @@
 {
 public:
     inline LightRefBase() : mCount(0) { }
-    inline void incStrong(const void* id) const {
+    inline void incStrong(__attribute__((unused)) const void* id) const {
         android_atomic_inc(&mCount);
     }
-    inline void decStrong(const void* id) const {
+    inline void decStrong(__attribute__((unused)) const void* id) const {
         if (android_atomic_dec(&mCount) == 1) {
             delete static_cast<const T*>(this);
         }