[llvm] [AArch64][SVE] Avoid extra pop of "FixedObject" with FPAfterSVECalleeSaves (PR #156452)

[Benjamin Maxwell via llvm-commits]

MacDue wrote:

Kind ping. Rebased with fixed the diff. I think it's probably worth fixing this miscompile. 

https://github.com/llvm/llvm-project/pull/156452