[llvm] [AMDGPU] Fix leak and self-assignment in copy assignment operator (PR #107847)

[Fraser Cormack via llvm-commits]

frasercrmck wrote:

> Looks good to me. Thanks!
> 
> Which tool did you use to catch this bug?

Thanks! It's an Intel internal static analysis tool.

https://github.com/llvm/llvm-project/pull/107847