[llvm] [AArch64][SME] Conditionally do smstart/smstop (PR #77113)

[Sander de Smalen via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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sdesmalen-arm wrote:

nit: Just one final little nit on the name of this file, can you rename it to: `sme-streaming-body-streaming-compatible-interface.ll`

https://github.com/llvm/llvm-project/pull/77113