[llvm] Do not use R12 for indirect tail calls with PACBTI (PR #82661)

[Eleanor Bonnici via llvm-commits]

eleanor-arm wrote:

I think what clang needs to generate is 
```
!4 = !{i32 8, !"sign-return-address", i32 1}                                                                                             
!5 = !{i32 8, !"sign-return-address-all", i32 1} 
``` 
then the codegen is correct. Would you agree? 

https://github.com/llvm/llvm-project/pull/82661