[llvm] [TableGen] Use consistent field kind checking in getNumericKey. (PR #83284)

[Piotr Sobczak via llvm-commits]

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

Thanks for the quick fix!

Normally it would need a test case, but I wasn't able to come up with a reproducer myself and I realize it can be tricky.

https://github.com/llvm/llvm-project/pull/83284