Fix unused-parameter warnings

These are exposed when frameworks/av/include is moved from being a
system include directory to a normal include directory.

Test: m -j checkbuild
Change-Id: I0e3787fbee70339f7dcbc979f448800ecfff0f17
diff --git a/include/media/ExtendedAudioBufferProvider.h b/include/media/ExtendedAudioBufferProvider.h
index 168ceed..51e4713 100644
--- a/include/media/ExtendedAudioBufferProvider.h
+++ b/include/media/ExtendedAudioBufferProvider.h
@@ -31,7 +31,7 @@
 
     // Invoked by buffer consumer when a new timestamp is available.
     // Default implementation ignores the timestamp.
-    virtual void    onTimestamp(const ExtendedTimestamp& timestamp) { }
+    virtual void    onTimestamp(const ExtendedTimestamp& /*timestamp*/) { }
 };
 
 }   // namespace android