intel/fs: Work around dual-source blending hangs in combination with SIMD16
It was found that dual-source blending hangs with SIMD16 dispatch in some specific but unknown situation. Which in the wild happen when rgba anti-aliasing is enabled for fonts.
Next Mesa release is close and a precise cause of the hang is still unknown, however it has considerable impact for users.
Also I'm not sure if gen12 is affected, could someone test it?