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/MonoPipe.cpp b/media/libnbaio/MonoPipe.cpp
index 3c61b60..b23967b 100644
--- a/media/libnbaio/MonoPipe.cpp
+++ b/media/libnbaio/MonoPipe.cpp
@@ -30,7 +30,7 @@
 
 namespace android {
 
-MonoPipe::MonoPipe(size_t reqFrames, NBAIO_Format format, bool writeCanBlock) :
+MonoPipe::MonoPipe(size_t reqFrames, const NBAIO_Format& format, bool writeCanBlock) :
         NBAIO_Sink(format),
         mUpdateSeq(0),
         mReqFrames(reqFrames),