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/MonoPipe.h b/include/media/nbaio/MonoPipe.h
index d3802fe..b09b35f 100644
--- a/include/media/nbaio/MonoPipe.h
+++ b/include/media/nbaio/MonoPipe.h
@@ -41,7 +41,7 @@
     // Note: whatever shares this object with another thread needs to do so in an SMP-safe way (like
     // creating it the object before creating the other thread, or storing the object with a
     // release_store). Otherwise the other thread could see a partially-constructed object.
-    MonoPipe(size_t reqFrames, NBAIO_Format format, bool writeCanBlock = false);
+    MonoPipe(size_t reqFrames, const NBAIO_Format& format, bool writeCanBlock = false);
     virtual ~MonoPipe();
 
     // NBAIO_Port interface