[llvm] LoongArch: Set FMAXNUM and FMINNUM as Legal (PR #139010)

[via llvm-commits]

tangaac wrote:

Files optimized on llvm-test-suite after this pr can be found here
https://github.com/tangaac/loong-opt-cov-ts/commit/d98d5ee1e5079eec5d1741b0dad99a7a1ba58a90


https://github.com/llvm/llvm-project/pull/139010