[llvm] [LoopIdiom] Update MemorySSA when optimizing CRC with lookup table (PR #213054)

[Sean Clarke via llvm-commits]

xarkenz wrote:

The included `cyclic-redundancy-check-memoryssa.ll` was the best I could come up with. Both commits only pass with their respective builds. I couldn't figure out a way to have UTC generate the test, but hopefully this is sufficient.

https://github.com/llvm/llvm-project/pull/213054