[X86][SSE] canonicalizeShuffleMaskWithHorizOp - simplify...

[X86][SSE] canonicalizeShuffleMaskWithHorizOp - simplify shuffle(HOP(HOP(X,Y),HOP(Z,W))) style chains.

See if we can remove the shuffle by resorting a HOP chain so that the HOP args are pre-shuffled.

This initial version just handles (the most common) v4i32/v4f32 hadd/hsub reduction patterns - future work can extend this to v8i16 types plus PACK chains (2f64 HADD/HSUB should already be handled in the half-lane combine code later on).