Moving Extensions codecs to net/flow to avoid circular dependencies

Change-Id: I93dc5580ff46f57afe93dd4d1f0217359d5c89c2
diff --git a/core/common/src/main/java/org/onosproject/codec/impl/EncodeInstructionCodecHelper.java b/core/common/src/main/java/org/onosproject/codec/impl/EncodeInstructionCodecHelper.java
index 2727223..8f5fc74 100644
--- a/core/common/src/main/java/org/onosproject/codec/impl/EncodeInstructionCodecHelper.java
+++ b/core/common/src/main/java/org/onosproject/codec/impl/EncodeInstructionCodecHelper.java
@@ -20,7 +20,7 @@
 import org.onlab.osgi.ServiceDirectory;
 import org.onlab.util.HexString;
 import org.onosproject.codec.CodecContext;
-import org.onosproject.codec.ExtensionTreatmentCodec;
+import org.onosproject.net.flow.ExtensionTreatmentCodec;
 import org.onosproject.net.Device;
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.OchSignal;