[llvm] Fix parentheses for clarity in X86ISelLowering.cpp (PR #121954)

[via llvm-commits]

soumyaGhoshh wrote:

got it, very sorry i didn't read all through the building or contribution guides. I'm again checking for it. I built the whole LLVM locally which took a lot of time and resources u know, thanks for guiding with building only the target i''l try and revert to you 

https://github.com/llvm/llvm-project/pull/121954