[llvm] [RISCV] Limit VLEN in getOptimalMemOpType to prevent creating invalid MVTs. (PR #139116)

[Craig Topper via llvm-commits]

topperc wrote:

> LGTM.
> 
> Please add a test if you can reduce one.

I made one, but I forgot `git add`. Brain fog from moving I guess.

https://github.com/llvm/llvm-project/pull/139116