Added copyright header to demo P4 programs

Change-Id: Ifa5c80db6cffae56e3666a60f3c0f40d456f443c
diff --git a/tools/test/p4src/p4-16/include/checksums.p4 b/tools/test/p4src/p4-16/include/checksums.p4
index effab74..f59089a 100644
--- a/tools/test/p4src/p4-16/include/checksums.p4
+++ b/tools/test/p4src/p4-16/include/checksums.p4
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2017-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #ifndef CHECKSUMS
 #define CHECKSUMS
 #include "headers.p4"