[llvm] [PatternMatch] Allow `m_ConstantInt` to match integer splats (PR #153692)

[Yingwei Zheng via llvm-commits]

https://github.com/dtcxzyw commented:

`m_ConstantInt` is intended to match a scalar. We may need a separate matcher to handle constant splats.

https://github.com/llvm/llvm-project/pull/153692