[llvm] [X86] combineVTRUNCSAT - don't split 128-bit concatenated vectors when folding to PACKSS/US (PR #194347)

[Phoebe Wang via llvm-commits]

phoebewang wrote:

> If the VTRUNCS/US node has 128-bit src/dst types

This reads as either one has 128-bit type.

https://github.com/llvm/llvm-project/pull/194347