[llvm] TargetInstrInfo: squelch a signedness warning on MSVC (PR #74078)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

Thanks. I looked at the build log, and all the warnings are coming from including MCInstrItineraries.h, and the warning is on line 223, which I've fixed. 

https://github.com/llvm/llvm-project/pull/74078