Adding AUTHORS and changing copyright headers to refer to it.

Change-Id: Id3306370911baf01bd2137dc0fbc8c421682e9f7
diff --git a/inc/hf/arch/timer.h b/inc/hf/arch/timer.h
index 935a9f4..f226020 100644
--- a/inc/hf/arch/timer.h
+++ b/inc/hf/arch/timer.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2018 Google LLC
+ * Copyright 2018 The Hafnium Authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.