[llvm] [AArch64][SME] Propagate desired ZA states in the MachineSMEABIPass (PR #149510)

[Sam Tebbs via llvm-commits]

https://github.com/SamTebbs33 approved this pull request.

I'm not too familiar with ZA state changes, but in general the code itself looks good to me.

https://github.com/llvm/llvm-project/pull/149510