Relicense Hafnium under the BSD 3 clause license.

Updates to the rest of the links in the documentation will follow in a
separate patch.

Change-Id: I52e35dad8fa12be48df5459a5fc8521adc53d55b
Signed-off-by: Andrew Walbran <qwandor@google.com>
diff --git a/build/linux/linux.gni b/build/linux/linux.gni
index 952bedc..65cc9df 100644
--- a/build/linux/linux.gni
+++ b/build/linux/linux.gni
@@ -1,16 +1,8 @@
 # Copyright 2019 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.
-# You may obtain a copy of the License at
-#
-#     https://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.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://opensource.org/licenses/BSD-3-Clause.
 
 template("source_dir") {
   action("${target_name}") {