[ GPU ] Enable x86 OpenCL with some fixes

[EunjuYang]

• Current OpenCL option is not fully enabled for x86 environment.
• Even with [ GPGPU ] enable X86 OpenCL with some fixes #2727, we may face some build error like:

/home/donghak/Desktop/workspace/nntrainer/nntrainer/opencl/opencl_program.cpp:73:10: error: variable length array ‘binaries_size’ is used [-Werror=vla]
   73 |   size_t binaries_size[num_devices];
      |          ^~~~~~~~~~~~~
/home/donghak/Desktop/workspace/nntrainer/nntrainer/opencl/opencl_program.cpp:98:8: error: variable length array ‘kernel_names’ is used [-Werror=vla]
   98 |   char kernel_names[kernel_names_size];
      |        ^~~~~~~~~~~~
/home/donghak/Desktop/workspace/nntrainer/nntrainer/opencl/opencl_program.cpp:113:18: error: variable length array ‘binaries_ptr’ is used [-Werror=vla]
  113 |   unsigned char *binaries_ptr[num_devices];

as mesntioned in #2770.

• In order to fully enable OpenCL for x86 environment, some compilation error should be handled.

[taos-ci]

cibot: Thank you for posting issue #2776. The person in charge will reply soon.

[EunjuYang]

#2727 is resolving this issue. It can be fixed after the PR is merged.

[EunjuYang]

Upon the resolving PR, it still has some build error for x86 without enable-fp16=true option. It needs to be fixed.