gfxstream: re-license cereal

While cereal implements an API provided by Khronos Apache 2.0
files, the files were started in AOSP, and can be relicensed to
MIT.

Reviewed-by: Aaron Ruby <aruby@blackberry.com>
Acked-by: Yonggang Luo <luoyonggang@gmail.com>
Acked-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27246>

src/gfxstream/codegen/scripts/cereal/transform.py

@@ -1,17 +1,5 @@
-# Copyright (c) 2018 The Android Open Source Project
-# Copyright (c) 2018 Google Inc.
-#
-# 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
-#
-#     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.
+# Copyright 2018 Google LLC
+# SPDX-License-Identifier: MIT
 
 from .common.codegen import CodeGen
 from .common.vulkantypes import \