Fix SmartspaceService callback comparison.

We should use binder references when comparing two IPC callbacks.

Test: Inject a test code into LocscreenSmartspaceController#reloadSmartspace() that register and unregister a test smartspace listener. Verify that the listeners is
get invoked without the fix and is not get invoked with the fix.
Change-Id: I3229c6496cde43ba1df65412857eb36b47b525c4

core/java/android/service/smartspace/SmartspaceService.java

@@ -302,7 +302,7 @@ public abstract class SmartspaceService extends Service {
                 Slog.e(TAG, "Callback is null, likely the binder has died.");
                 return false;
             }
-            return mCallback.equals(callback);
+            return mCallback.asBinder().equals(callback.asBinder());
         }
 
         @Override