* Add some tip description about enable OpenCL for benchmark_app. Signed-off-by: xipingya <xiping.yan@intel.com> * Export doesn't work, we need to add -Dopencl_root_hints=[PATH]/OpenCL-CLHPP/include to cmake command. Signed-off-by: xipingya <xiping.yan@intel.com> Co-authored-by: Chen Peter <peter.chen@intel.com>