[llvm] TwoAddressInstructions: Don't treat an undef use as a kill (PR #227309)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> The original problem is still there. `clang++ --target=x86_64-unknown-linux-gnu -m32 -O3 -std=c++26 -c f2s.cpp`
> 
> [f2s.cpp](https://github.com/user-attachments/files/32813740/f2s.cpp)

Which original problem? There were 2, this fixes the second one 

https://github.com/llvm/llvm-project/pull/227309