[X86] SimplifyDemandedVectorEltsForTargetNode - reduce the size of VPERMV v16f32/v16i32 nodes if the upper elements are not demanded (#134890)
Missed in #133923 - even without AVX512VL, we can replace VPERMV v16f32/v16i32 nodes with the AVX2 v8f32/v8i32 equivalents.