[llvm] [CostModel] Provide a default model for histogram intrinsics (PR #149348)

[Paschalis Mpeis via llvm-commits]

https://github.com/paschalis-mpeis approved this pull request.

Thanks, Graham, LGTM!

Up to you, but may be better to get another look from the reviewers if they are more active in vectorization / cost-modelling.

https://github.com/llvm/llvm-project/pull/149348