[llvm] [MIPS]Remove unnecessary SLL instructions on MIPS64el (PR #109386)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

I don't think this transform is correct: https://alive2.llvm.org/ce/z/-kNt7y

https://github.com/llvm/llvm-project/pull/109386