[llvm] [AMDGPU] Fix typo in promoteUniformOpToI32 (PR #109942)

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

There were no test updates, we either don't have the coverage or this somehow didn't cause any issue due to something else taking care of it?

https://github.com/llvm/llvm-project/pull/109942