fix remaining signing issues in treatments.

Change-Id: Id5ae44e529a516a4b2593778491ea16ca8dc7937
diff --git a/core/api/src/main/java/org/onosproject/net/flow/DefaultTrafficTreatment.java b/core/api/src/main/java/org/onosproject/net/flow/DefaultTrafficTreatment.java
index a551f79..049f49a 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/DefaultTrafficTreatment.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/DefaultTrafficTreatment.java
@@ -292,7 +292,7 @@
         }
 
         @Override
-        public Builder popMpls(Short etherType) {
+        public Builder popMpls(int etherType) {
             return add(Instructions.popMpls(etherType));
         }