[llvm] [LoopUnroll] Fix block frequencies for epilogue (PR #159163)

[Joel E. Denny via llvm-commits]

jdenny-ornl wrote:

> It looks like this is causing a crash for the `opt -passes='loop-unroll<O3>'`:

Thanks.  Is there a bot somewhere that shows the crash?

https://github.com/llvm/llvm-project/pull/159163