[llvm] [SelectionDAG] Support integer promotion for VP_LOAD and VP_STORE (PR #81299)

[zhijian lin via llvm-commits]

diggerlin wrote:

it looks the patch is target impendent, I run the  `llc llvm/test/CodeGen/RISCV/rvv/vpload.ll` in powerpc, it hit a error 

LLVM ERROR: Invalid size request on a scalable vector.

https://github.com/llvm/llvm-project/pull/81299