[llvm] [MIPS][ISel] Fix musttail (PR #161860)

[Khem Raj via llvm-commits]

kraj wrote:

> > Please squash changes into initial commit
> 
> Per "Contributing to LLVM" Policy, we do not do force-push (and squash), we rather use incremental changes to address comments during review process. And, once the pull request is approved, we select the “Squash and merge” button.

right, squashing is what I meant. 

https://github.com/llvm/llvm-project/pull/161860