[llvm] [RISCV] Move vnclip patterns into DAGCombiner. (PR #93728)

[Philip Reames via llvm-commits]

https://github.com/preames approved this pull request.

LGTM

Aside - This is starting to look a bit like isSaturatingMinMax in DAGCombine.  This version handles the _VL variants, and that one handles the select variants, so neither is a subset of the other.  Do we have any room to optimize the saturating fp_to_sint patterns the DAG is working on?  I don't see anything but figured it's worth asking..  Alternatively, is there anything we can do to optimize/recognize the clamp idiom on it's own?

https://github.com/llvm/llvm-project/pull/93728