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/Pipe.h b/include/media/nbaio/Pipe.h
index 79a4eee..c784129 100644
--- a/include/media/nbaio/Pipe.h
+++ b/include/media/nbaio/Pipe.h
@@ -30,7 +30,7 @@
 
 public:
     // maxFrames will be rounded up to a power of 2, and all slots are available. Must be >= 2.
-    Pipe(size_t maxFrames, NBAIO_Format format);
+    Pipe(size_t maxFrames, const NBAIO_Format& format);
     virtual ~Pipe();
 
     // NBAIO_Port interface