ONOS-7077 Openflow 1.5 OXS and stat trigger support

Change-Id: I006bcd3d8eac451a780c7e5c69a12298ead14281
diff --git a/core/api/src/main/java/org/onosproject/net/flow/instructions/Instruction.java b/core/api/src/main/java/org/onosproject/net/flow/instructions/Instruction.java
index c3c9b60..66fbb18 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/instructions/Instruction.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/instructions/Instruction.java
@@ -96,7 +96,12 @@
         /**
          * Signifies that an extension instruction will be used.
          */
-        EXTENSION
+        EXTENSION,
+
+        /**
+         * Signifies that statistics will be triggered.
+         */
+        STAT_TRIGGER
     }
 
     /**