SWDEV-293871 - Update license for edited Khronos headers

We should acknowledge that we modified third party files.

Change-Id: I510e445d049faafe06bb78353431d9427f3eb20c

opencl/khronos/headers/opencl1.2/CL/cl_ext.h

@@ -1,3 +1,4 @@
+/* Modifications Copyright (C) 2010-2021 Advanced Micro Devices, Inc. */
 /*******************************************************************************
  * Copyright (c) 2008-2015 The Khronos Group Inc.
  *

opencl/khronos/headers/opencl2.0/CL/cl_ext.h

@@ -1,3 +1,4 @@
+/* Modifications Copyright (C) 2010-2021 Advanced Micro Devices, Inc. */
 /*******************************************************************************
  * Copyright (c) 2008-2015 The Khronos Group Inc.
  *

opencl/khronos/headers/opencl2.1/CL/cl_ext.h

@@ -1,3 +1,4 @@
+/* Modifications Copyright (C) 2010-2021 Advanced Micro Devices, Inc. */
 /*******************************************************************************
  * Copyright (c) 2008-2015 The Khronos Group Inc.
  *

opencl/khronos/headers/opencl2.2/CL/cl_ext.h

@@ -1,3 +1,4 @@
+/* Modifications Copyright (C) 2010-2021 Advanced Micro Devices, Inc. */
 /*******************************************************************************
  * Copyright (c) 2008-2019 The Khronos Group Inc.
  *