[SYCL][USM] fix clMemFreeIntel ptr argument

[hiaselhans]

Compiling llvm from 0 (using cmake to download opencl headers) fails with the following message:

In file included from ~/dev/gpu/llvm/sycl/include/CL/sycl/detail/pi.h:49,
                 from ~/dev/gpu/llvm/sycl/include/CL/sycl/exception.hpp:15,
                 from ~/dev/gpu/llvm/sycl/include/CL/sycl/detail/common.hpp:121,
                 from ~/dev/gpu/llvm/sycl/include/CL/sycl/aliases.hpp:11,
                 from ~/dev/gpu/llvm/sycl/include/CL/sycl/detail/generic_type_traits.hpp:12,
                 from ~/dev/gpu/llvm/sycl/source/detail/builtins_helper.hpp:10,
                 from ~/dev/gpu/llvm/sycl/source/detail/builtins_common.cpp:18:
~/dev/gpu/llvm/sycl/include/CL/cl_usm_ext.h:125:21: error: conflicting declaration 'typedef cl_int (* clMemFreeINTEL_fn)(cl_context, const void*)'
  125 | cl_int(CL_API_CALL *clMemFreeINTEL_fn)(cl_context context,
      |                     ^~~~~~~~~~~~~~~~~
In file included from ~/dev/gpu/llvm/sycl/include/CL/sycl/detail/common.hpp:11,
                 from ~/dev/gpu/llvm/sycl/include/CL/sycl/aliases.hpp:11,
                 from ~/dev/gpu/llvm/sycl/include/CL/sycl/detail/generic_type_traits.hpp:12,
                 from ~/dev/gpu/llvm/sycl/source/detail/builtins_helper.hpp:10,
                 from ~/dev/gpu/llvm/sycl/source/detail/builtins_common.cpp:18:
tools/sycl/OpenCL/inc/CL/cl_ext_intel.h:533:1: note: previous declaration as 'typedef cl_int (* clMemFreeINTEL_fn)(cl_context, void*)'
  533 | clMemFreeINTEL_fn)(
      | ^~~~~~~~~~~~~~~~~

It seems to relate to a commit in OpenCL-Headers
where clMemFreeIntel is defined as void* instead of const void*:
https://github.com/KhronosGroup/OpenCL-Headers/blob/b04034a17e214322772c19e7ccd2adf0cd306920/CL/cl_ext_intel.h#L530

This PR changes the arguments from const void* -> void*
It is untested but compiles again.

[bader]

Thanks!
I think @againull addressed this problem in #1852.

[hiaselhans]

oh!

perfect then! thanks for the fix :)