[llvm] [CodeGen] Update for scalable MemoryType in MMO (PR #70452)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

The reason the MMO uses an LLT is we also need the number of vector elements to correctly legalize vector loads and stores. Doesn't switching that to LocationSize lose that information?

https://github.com/llvm/llvm-project/pull/70452