Switch to MIT license.

BUG=31508897
TEST=Unit tests pass.

Change-Id: I790afce2889e3dfaf6a53c02ccaaec3544229a9c
diff --git a/libavb/avb_hashtree_descriptor.c b/libavb/avb_hashtree_descriptor.c
index 3a79eb7..fe4de6d 100644
--- a/libavb/avb_hashtree_descriptor.c
+++ b/libavb/avb_hashtree_descriptor.c
@@ -1,17 +1,25 @@
 /*
  * Copyright (C) 2016 The Android Open Source Project
  *
- * 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
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
  *
- *      http://www.apache.org/licenses/LICENSE-2.0
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
  *
- * 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.
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
  */
 
 #include "avb_hashtree_descriptor.h"