binder: MemoryHeapIon: fix unused parameters

Using the __attribute__((unused)) preprocessor directive

Change-Id: I29d27fd7eacb962ffa06ccd81ee48b48f3743243
Merge commit 'refs/changes/09/80409/1' of http://review.cyanogenmod.org/CyanogenMod/android_frameworks_native into cm-12.0