[llvm] [ARM] Auto-decode s_cc_out operand (PR #159956)

[Simon Tatham via llvm-commits]

https://github.com/statham-arm approved this pull request.

I like it. Less code, and avoids the uncondition calls to `instrInITBlock` and `AddThumb1SBit` even in cases where they're not relevant.

For a moment I thought you'd managed to remove those two `mutable` fields, which would have been even nicer! But then I realised you'd just had to move them from the private to the public section.

https://github.com/llvm/llvm-project/pull/159956