Add license section to cache_dir_probe.bt

Added license information to the cache_dir_probe.bt file.

Author: moonchen

tests/gold_tests/ats_probe_cache_dir/cache_dir_probe.bt

@@ -3,7 +3,24 @@
 
   Trace cache directory SystemTap probes.
 
-*/
+  @section license License
+
+  Licensed to the Apache Software Foundation (ASF) under one
+  or more contributor license agreements.  See the NOTICE file
+  distributed with this work for additional information
+  regarding copyright ownership.  The ASF licenses this file
+  to you 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.
+ */
 
 BEGIN
 {