X86: If SSE4.1 is missing lower SMUL_LOHI of v4i32 to pmuludq and fix up the high parts.

This is more expensive than pmuldq but still cheaper than scalarizing the whole thing.
X86TTI: Adjust sdiv cost now that we can lower it on plain SSE2.

Includes a fix for a horrible typo that caused all SDIV costs to be
slightly off :)