[X86][SSE] Always combine target shuffles to MOVSD/MOVSS

[X86][SSE] Always combine target shuffles to MOVSD/MOVSS

Now we can commute to BLENDPD/BLENDPS on SSE41+ targets if necessary, so simplify the combine matching where we can.

This required me to add a couple of scalar math movsd/moss fold patterns that hadn't been needed in the past.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283038 91177308-0d34-0410-b5e6-96231b3b80d8