Avoid use of Objects.hash when there's only 1 params

- directly call #hashCode() when hashed Object seems non-null
- replace with Objects.hashCode(Object) when Nullable
- replace with Long.hashCode(long), etc. when primitive

Change-Id: I08c24ebbe94cf4162d1491209a14baf953163e41
diff --git a/ovsdb/api/src/main/java/org/onosproject/ovsdb/controller/OvsdbPortNumber.java b/ovsdb/api/src/main/java/org/onosproject/ovsdb/controller/OvsdbPortNumber.java
index bd094d0..86fc887 100644
--- a/ovsdb/api/src/main/java/org/onosproject/ovsdb/controller/OvsdbPortNumber.java
+++ b/ovsdb/api/src/main/java/org/onosproject/ovsdb/controller/OvsdbPortNumber.java
@@ -47,7 +47,7 @@
 
     @Override
     public int hashCode() {
-        return Objects.hash(value);
+        return Objects.hashCode(value);
     }
 
     @Override