Use const NBAIO_Format& in parameter lists

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

Change-Id: I8d73a6b29580c65105afd78f24db7e2f4a1eb872
diff --git a/media/libnbaio/Pipe.cpp b/media/libnbaio/Pipe.cpp
index 1c21f9c..115f311 100644
--- a/media/libnbaio/Pipe.cpp
+++ b/media/libnbaio/Pipe.cpp
@@ -25,7 +25,7 @@
 
 namespace android {
 
-Pipe::Pipe(size_t maxFrames, NBAIO_Format format) :
+Pipe::Pipe(size_t maxFrames, const NBAIO_Format& format) :
         NBAIO_Sink(format),
         mMaxFrames(roundup(maxFrames)),
         mBuffer(malloc(mMaxFrames * Format_frameSize(format))),