[clang, hexagon] Update copyright, license text (#107161)

When this file was first contributed - `28b01c59c93d ([hexagon] Add
{hvx,}hexagon_{protos,circ_brev...}, 2021-06-30)` - I incorrectly
included a QuIC copyright statement with "All rights reserved". I should
have contributed this file with the `Apache+LLVM exception` license.

Author: androm3da

clang/lib/Headers/hexagon_types.h

@@ -1,7 +1,11 @@
-/******************************************************************************/
-/*   (c) 2020 Qualcomm Innovation Center, Inc. All rights reserved.           */
-/*                                                                            */
-/******************************************************************************/
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
 #ifndef HEXAGON_TYPES_H
 #define HEXAGON_TYPES_H