[compiler-rt] [compiler-rt][Mips] Fix mips SP register definition (PR #124493)

[Vitaly Buka via llvm-commits]

vitalybuka wrote:

> > Please undo reformat, or extract into a separate commit or PR
> 
> Sorry, I was following https://llvm.org/docs/Contributing.html#how-to-submit-a-patch which says to use `git clang-format HEAD~1` and amend the commit - I am a bit confused, is this not up to date anymore?

That's relevant, but it assume the pre-existing code  is already clang formatted.

But there is "be an isolated change. Independent changes should be submitted as separate patches as this makes reviewing easier."

This file have legacy formatting, which we incrementally change to new format.
So we have 2 interdependent changes, format legacy code, and Mips change.

https://github.com/llvm/llvm-project/pull/124493