isl: disable mcs (and mcs+ccs) for color msaa on DG2
Fixes lots of various test failures in: dEQP-VK.pipeline.multisample.min_sample_shading_disabled.* dEQP-GLES3.functionalmultisample. KHR-GLsample_variables.
Signed-off-by: Tapani Pälli tapani.palli@intel.com