clc, rusticl: add support for cl_khr_subgroup_shuffle and shuffle_relative
Seems like this just works in gallium and I think it's not needed to add any new caps as drivers can just flip the nir_lower_subgroups
flags. OpenCL subgroup support is hidden behind PIPE_COMPUTE_CAP_SUBGROUP_SIZES
and PIPE_COMPUTE_CAP_MAX_SUBGROUPS
.