[llvm] [AMDGPU] Fix amdgcn.mbcnt known bits conflicting with the range attribute (PR #227725)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Hi @nikic and @ruiling, can you please review these changes and share your thoughts. If there's no further feedback by this weekend, I'll go ahead and merge it.

You don't need to get a review from everyone listed in reviewers 

https://github.com/llvm/llvm-project/pull/227725