[llvm] [LoongArch] Use div.w/mod.w to eliminate unnecessary sign-extend for sdiv/srem i32. (PR #117298)

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https://github.com/heiher approved this pull request.

LGTM. This is helpful for eliminating unnecessary sign extensions. There are no test cases for this because the OptW pass already performs similar optimizations.

https://github.com/llvm/llvm-project/pull/117298