Skip sub_group_dispatch. (#864)
Skip sub_group_dispatch. (#864)

* Skip sub_group_dispatch.

If sub groups aren't supported, skip the test.

* Do not test for cl_khr_subgroups as the extension requires IFP.

3.0 allows sub groups *without* IFP so the check was invalid.
KhronosGroup/OpenCL-CTS,KhronosGroup/OpenCL-CTS,KhronosGroup/OpenCL-CTS,KhronosGroup/OpenCL-CTS