Use const NBAIO_Format& in parameter lists

This is in preparation for changing the typedef to a struct.

Change-Id: I8d73a6b29580c65105afd78f24db7e2f4a1eb872
diff --git a/include/media/nbaio/AudioBufferProviderSource.h b/include/media/nbaio/AudioBufferProviderSource.h
index 2c4aaff..b16e20a 100644
--- a/include/media/nbaio/AudioBufferProviderSource.h
+++ b/include/media/nbaio/AudioBufferProviderSource.h
@@ -27,7 +27,7 @@
 class AudioBufferProviderSource : public NBAIO_Source {
 
 public:
-    AudioBufferProviderSource(AudioBufferProvider *provider, NBAIO_Format format);
+    AudioBufferProviderSource(AudioBufferProvider *provider, const NBAIO_Format& format);
     virtual ~AudioBufferProviderSource();
 
     // NBAIO_Port interface