Rather than having a different custom legalization

Rather than having a different custom legalization
hook for each way in which a result type can be
legalized (promotion, expansion, softening etc),
just use one: ReplaceNodeResults, which returns
a node with exactly the same result types as the
node passed to it, but presumably with a bunch of
custom code behind the scenes.  No change if the
new LegalizeTypes infrastructure is not turned on.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53137 91177308-0d34-0410-b5e6-96231b3b80d8