[llvm] [mlir] mlir/MathExtras: consolidate with llvm/MathExtras (PR #95087)

[Mehdi Amini via llvm-commits]

https://github.com/joker-eph approved this pull request.

LGTM on the principle, @nikic find some issues to fix of course.
This is NFC right?

https://github.com/llvm/llvm-project/pull/95087