[llvm] [AArch64] Support scalable vp.udiv/vp.sdiv with SVE (PR #154327)

[Luke Lau via llvm-commits]

lukel97 wrote:

I should also mention that the AArch64 backend is not my neck of the woods at all, and the original PR for RISC-V in https://github.com/llvm/llvm-project/pull/154076 isn't blocked by this. 

Happy to go with whatever the actual AArch64 people here think is the right direction, just thought I'd post this patch as a sort of proof-of-concept if others found it interesting!

https://github.com/llvm/llvm-project/pull/154327