[llvm] [SimplifyCFG] Fix the compile crash for invalid upper bound value (PR #71351)

[via llvm-commits]

vfdff wrote:

Thanks for @nikic and  @zmodem.

If `the type of TableSize` is uint64_t （uint64_t TableSize），then it will still wrap for `the uint64_t type index of switch` ?
So ignore it now with `CR.getUpper() > CR.getLower()` may be more simple?

https://github.com/llvm/llvm-project/pull/71351