Get CPU port dynamically in fabric interpreter

Different HW platforms have different CPU ports, here we allow using
the same interpreter with multiple platform.

Change-Id: I0895d4d3e11560c75aca3fa908ca38759b597d67
diff --git a/core/api/src/main/java/org/onosproject/net/pi/model/PiPipeconf.java b/core/api/src/main/java/org/onosproject/net/pi/model/PiPipeconf.java
index 9b353c8..5fedaf7 100644
--- a/core/api/src/main/java/org/onosproject/net/pi/model/PiPipeconf.java
+++ b/core/api/src/main/java/org/onosproject/net/pi/model/PiPipeconf.java
@@ -100,6 +100,14 @@
         /**
          * Barefoot's Tofino context JSON.
          */
-        TOFINO_CONTEXT_JSON
+        TOFINO_CONTEXT_JSON,
+
+        /**
+         * CPU port file in UTF 8 encoding.
+         */
+        // TODO: consider a better way to get the CPU port in the interpreter
+        // (see FabricInterpreter.java mapLogicalPortNumber). Perhaps using
+        // pipeconf annotations?
+        CPU_PORT_TXT
     }
 }