intel/compiler: use sampler for constant loads on snb too
Enable using the sampler for constant loads on snb, fixing the failure of the piglit tests "vs-float-array-variable-index" and "gs-float-array-variable-index".
Enable using the sampler for constant loads on snb, fixing the failure of the piglit tests "vs-float-array-variable-index" and "gs-float-array-variable-index".