Add AMediaFormat functions to clear and copy

Also move NdkMediaFormat internals to libmedia to avoid a future circular
dependency between libmedia and libmediandk.

Bug: 111407253
Test: build, boot, play some files

Change-Id: I54d91439f216c3834726e5505afef40dc0d93e67
diff --git a/media/ndk/NdkMediaMuxer.cpp b/media/ndk/NdkMediaMuxer.cpp
index dffc4d7..b213fa9 100644
--- a/media/ndk/NdkMediaMuxer.cpp
+++ b/media/ndk/NdkMediaMuxer.cpp
@@ -20,7 +20,7 @@
 
 #include <media/NdkMediaMuxer.h>
 #include <media/NdkMediaCodec.h>
-#include "NdkMediaFormatPriv.h"
+#include <media/NdkMediaFormatPriv.h>
 
 
 #include <utils/Log.h>