[llvm] [AArch64][SME] Introduce CHECK_MATCHING_VL pseudo for streaming transitions (PR #157510)

[Gaëtan Bossu via llvm-commits]

https://github.com/gbossu commented:

It all looks sane to me, but I'm yet to thoroughly look at the tests. I just left a couple of nits so far, address as you please :)

https://github.com/llvm/llvm-project/pull/157510