[llvm] s390x: pattern match saturated truncation (PR #155377)

[Ulrich Weigand via llvm-commits]

https://github.com/uweigand commented:

Looks all good to me.  Only remaining question is whether we can drop the `IntegerMinMaxVectorOps` patterns now - if the tests still all pass, we should just do it as part of this patch.

https://github.com/llvm/llvm-project/pull/155377