[llvm] [Mips][NFC] Garbage collect unused code (PR #85499)

[Brad Smith via llvm-commits]

brad0 wrote:

> Go ahead please. I left these lines as I thought that they will be useful if we'd like to support `-mabicalls -mno-shared` in future.

It's not that I would try to dissuade you from adding support if desirable. It's just as MaskRay said usually code is not left in like that. You can always re-add it as necessary.

https://github.com/llvm/llvm-project/pull/85499