transcoding: check API31 as it's available

bug: 178144708
test: unit tests; atest MediaTranscodeManagerTest
Change-Id: Idee97e5596bfe599fb294e7b71b50514ac941ead
diff --git a/services/mediatranscoding/MediaTranscodingService.cpp b/services/mediatranscoding/MediaTranscodingService.cpp
index 8b64134..e387800 100644
--- a/services/mediatranscoding/MediaTranscodingService.cpp
+++ b/services/mediatranscoding/MediaTranscodingService.cpp
@@ -24,6 +24,7 @@
 #include <cutils/properties.h>
 #include <media/TranscoderWrapper.h>
 #include <media/TranscodingClientManager.h>
+#include <media/TranscodingDefs.h>
 #include <media/TranscodingLogger.h>
 #include <media/TranscodingResourcePolicy.h>
 #include <media/TranscodingSessionController.h>