[llvm] [AArch64] Use CMN instruction for negative SUBS immediates (PR #221398)

[Mugundan S via llvm-commits]

MGN-GIT wrote:

Hi @davemgreen 

A gentle ping to take a look this patch, please feel free to add your review comments and I am happy to work on the changes if any.

Thanks :)

https://github.com/llvm/llvm-project/pull/221398