Remove dependencies of libcpu_extension.so

[Corsair-cxs]

What problem does this feature solve?

In the OpenVINO 2020.3 release, the CPU extensions library were removed as they were moved into the plugin. It' would be improper to link target libraries of libcpu_extension.so

reference

https://community.intel.com/t5/Intel-Distribution-of-OpenVINO/Where-are-the-libcpu-extension-so-files-of-OpenVINO-Toolkit-2020/td-p/1183643