[X86] Make movsd commutable to shufpd with a 0x02 immediate on pre-SSE4.1 targets.

This can help avoid a copy or enable load folding.

On SSE4.1 targets we can commute it to blendi instead.

I had to make shufpd with a 0x02 immediate commutable as well
since we expect commuting to be reversible.

llvm-svn: 365292