Update OpenCL headers

* Make changes to include CL/opencl.hpp
* Update CL C++ header to v2.0.15
* Update CL Headers to v2021.06.30
* Resolves MLCE-665

Change-Id: Ie2896e213519003531ecff0889d2112838d72d1b
Signed-off-by: Pablo Marquez Tello <pablo.tello@arm.com>
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/c/VisualCompute/ComputeLibrary/+/377282
Tested-by: bsgcomp <bsgcomp@arm.com>
Reviewed-by: Sheri Zhang <sheri.zhang@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/6751
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/include/CL/cl_d3d11.h b/include/CL/cl_d3d11.h
index 10023dd..50ed906 100644
--- a/include/CL/cl_d3d11.h
+++ b/include/CL/cl_d3d11.h
@@ -75,7 +75,7 @@
 
 /******************************************************************************/
 
-typedef CL_API_ENTRY cl_int (CL_API_CALL *clGetDeviceIDsFromD3D11KHR_fn)(
+typedef cl_int (CL_API_CALL *clGetDeviceIDsFromD3D11KHR_fn)(
     cl_platform_id             platform,
     cl_d3d11_device_source_khr d3d_device_source,
     void *                     d3d_object,
@@ -84,27 +84,27 @@
     cl_device_id *             devices,
     cl_uint *                  num_devices) CL_API_SUFFIX__VERSION_1_2;
 
-typedef CL_API_ENTRY cl_mem (CL_API_CALL *clCreateFromD3D11BufferKHR_fn)(
+typedef cl_mem (CL_API_CALL *clCreateFromD3D11BufferKHR_fn)(
     cl_context     context,
     cl_mem_flags   flags,
     ID3D11Buffer * resource,
     cl_int *       errcode_ret) CL_API_SUFFIX__VERSION_1_2;
 
-typedef CL_API_ENTRY cl_mem (CL_API_CALL *clCreateFromD3D11Texture2DKHR_fn)(
+typedef cl_mem (CL_API_CALL *clCreateFromD3D11Texture2DKHR_fn)(
     cl_context        context,
     cl_mem_flags      flags,
     ID3D11Texture2D * resource,
     UINT              subresource,
     cl_int *          errcode_ret) CL_API_SUFFIX__VERSION_1_2;
 
-typedef CL_API_ENTRY cl_mem (CL_API_CALL *clCreateFromD3D11Texture3DKHR_fn)(
+typedef cl_mem (CL_API_CALL *clCreateFromD3D11Texture3DKHR_fn)(
     cl_context        context,
     cl_mem_flags      flags,
     ID3D11Texture3D * resource,
     UINT              subresource,
     cl_int *          errcode_ret) CL_API_SUFFIX__VERSION_1_2;
 
-typedef CL_API_ENTRY cl_int (CL_API_CALL *clEnqueueAcquireD3D11ObjectsKHR_fn)(
+typedef cl_int (CL_API_CALL *clEnqueueAcquireD3D11ObjectsKHR_fn)(
     cl_command_queue command_queue,
     cl_uint          num_objects,
     const cl_mem *   mem_objects,
@@ -112,7 +112,7 @@
     const cl_event * event_wait_list,
     cl_event *       event) CL_API_SUFFIX__VERSION_1_2;
 
-typedef CL_API_ENTRY cl_int (CL_API_CALL *clEnqueueReleaseD3D11ObjectsKHR_fn)(
+typedef cl_int (CL_API_CALL *clEnqueueReleaseD3D11ObjectsKHR_fn)(
     cl_command_queue command_queue,
     cl_uint          num_objects,
     const cl_mem *   mem_objects,