transcoding: check API31 as it's available

bug: 178144708
test: unit tests; atest MediaTranscodeManagerTest
Change-Id: Idee97e5596bfe599fb294e7b71b50514ac941ead
diff --git a/media/libmediatranscoding/TranscodingThermalPolicy.cpp b/media/libmediatranscoding/TranscodingThermalPolicy.cpp
index 9984abe..88f445c 100644
--- a/media/libmediatranscoding/TranscodingThermalPolicy.cpp
+++ b/media/libmediatranscoding/TranscodingThermalPolicy.cpp
@@ -17,6 +17,7 @@
 //#define LOG_NDEBUG 0
 #define LOG_TAG "TranscodingThermalPolicy"
 
+#include <media/TranscodingDefs.h>
 #include <media/TranscodingThermalPolicy.h>
 #include <media/TranscodingUidPolicy.h>
 #include <utils/Log.h>