[llvm] [AMDGPU][SIInsertWaitcnts] Do not add s_waitcnt when the counters are known to be 0 already (PR #72830)

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

gentle ping
If possible I'd like to land this before I'm OOO (next 2 weeks), if it's not possible to review this today or tomorrow let me know :)

https://github.com/llvm/llvm-project/pull/72830