[llvm] RISCV: Implement isLoadFromStackSlot/isStoreToStackSlot for rvv (PR #120524)

[Philip Reames via llvm-commits]

preames wrote:

My adopted version of this (https://github.com/llvm/llvm-project/pull/132296), has landed.  I went back to check if the differences in MemBytes setup were material, and the test changes from this change on tip of tree are the same as my landed change.  So, to my knowledge, no further work needed here.

https://github.com/llvm/llvm-project/pull/120524