[llvm] [CodeGen] NFC: Change order of checks in MachineInstr->isDead() (PR #124207)

[Nikita Popov via llvm-commits]

https://github.com/nikic approved this pull request.

LGTM, this does help: https://llvm-compile-time-tracker.com/compare.php?from=eda16991adeb078647b2d239fcf666ddece5c30a&to=bedd58f56dce1431f7d2396696c02534938ab7dd&stat=instructions:u

https://github.com/llvm/llvm-project/pull/124207