[llvm] [AArch64][SME] Rework VG CFI information for streaming-mode changes (PR #152283)

[Benjamin Maxwell via llvm-commits]

MacDue wrote:

See [sme-streaming-mode-changes-unwindinfo.ll](https://github.com/llvm/llvm-project/blob/9647e6b52f19b2441fbccf7df77fe6a1176d3eed/llvm/test/CodeGen/AArch64/sme-streaming-mode-changes-unwindinfo.ll) for a new test that shows the unwind information in a variety of cases. 

https://github.com/llvm/llvm-project/pull/152283