[X86] Move all the FP_TO_XINT/XINT_TO_FP setOperationActions into the same...

[X86] Move all the FP_TO_XINT/XINT_TO_FP setOperationActions into the same !useSoftFloat block. Qualify all of the Promote actions for these with !useSoftFloat too. NFCI

The Promote action doesn't apply until LegalizeDAG. By the time
we get there, we would have already softened all the FP operations
if useSoftFloat was true. So there wouldn't be any operation left
to Promote.