Adding AUTHORS and changing copyright headers to refer to it.

Change-Id: I3c2b83e7cd276fd875a497047c5c4f270625e856
diff --git a/qemu_aarch64/plat_entry.S b/qemu_aarch64/plat_entry.S
index 84fb281..95faec3 100644
--- a/qemu_aarch64/plat_entry.S
+++ b/qemu_aarch64/plat_entry.S
@@ -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.