Add missing license header

Signed-off-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>

Author: zaolin

pkg/intel/metadata/bg/bgkey/manifest_nocodegen.go

@@ -1,3 +1,7 @@
+// Copyright 2017-2023 the LinuxBoot Authors. All rights reserved
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package bgkey
 
 import (