[X86][SSE] Relax use limits for lowerAddSubToHorizontalOp (PR32433)

Now that we can use HADD/SUB for scalar additions from any pair of extracted elements (D61263), we can relax the one use limit as we will be able to merge multiple uses into using the same HADD/SUB op.

This exposes a couple of missed opportunities in LowerBuildVectorv4x32 which will be committed separately.

Differential Revision: https://reviews.llvm.org/D61782

llvm-svn: 360594