[lldb] Fix undefined behavior (#158119)
https://green.lab.llvm.org/job/llvm.org/view/LLDB/job/lldb-cmake-sanitized/2178/consoleText
```
[2025-09-11T13:10:53.352Z] /Users/ec2-user/jenkins/workspace/llvm.org/lldb-cmake-sanitized/llvm-project/lldb/source/Plugins/Instruction/ARM/EmulateInstructionARM.cpp:14138:35: runtime error: signed integer overflow: 2147483624 + 608 cannot be represented in type 'int32_t' (aka 'int')
[2025-09-11T13:10:53.352Z] SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /Users/ec2-user/jenkins/workspace/llvm.org/lldb-cmake-sanitized/llvm-project/lldb/source/Plugins/Instruction/ARM/EmulateInstructionARM.cpp:14138:35 in
```
