Revert "[DAGCombiner] avoid unnecessary indirection from SDNode/SDVal…

…ue; NFCI"

This reverts commit 21dadd7.

In at least PromoteIntBinOps, they wanted to know about users of *all* values
produced by the node not just the integer being promoted. For example not
replacing chain users if the operation was a load breaks the ordering of the
DAG.