[llvm] CodeGen: Remove redundant arguments to defusechain_instr_iterator (PR #135023)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **Apr 9, 12:21 PM EDT**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/135023).


https://github.com/llvm/llvm-project/pull/135023