[llvm] [LV] Ensure VPInstruction::usesFirstLaneOnly behaves correctly for WidePtrAdd (PR #169344)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Hmm, for a scalar plan, we should probably not emit a wide pointer add in the first place I think? 

https://github.com/llvm/llvm-project/pull/169344