[llvm] [TableGen] fix unreachable code warning in *GenSubtargetInfo.inc files (PR #182477)

[Rafał Rudnicki via llvm-commits]

bratpiorka wrote:

@jayfoad ok, I understand your point of view. Could you ping someone who can make the decision here? This is a simple change

https://github.com/llvm/llvm-project/pull/182477