[SelectionDAG] Remove the code that handles SETCC with a scalar result type from vector widening.

There's no such thing as a setcc with vector operands and scalar result. And if we're trying to widen the result we would have to already be looking at a vector result type.

So this patch renames the VSETCC function as the SETCC function and delete the original SETCC function.

llvm-svn: 319799