[llvm] [AArch64][GlobalISel] Ignore debug uses in mul-constant combine (PR #228100)

[via llvm-commits]

GopinathBalaji wrote:

I have read the linked policies, including the LLVM AI Tool Use Policy, and have noted my AI tool usage in the PR description. 
Since the issue #227648 was tagged `good-first-issue`, I used AI to only setup, search and learn. I wrote the fix myself.

https://github.com/llvm/llvm-project/pull/228100