[AMDGPU][Waitcnt] Re-apply fix "comparison of integers of different signs" build error"

Re-apply "[AMDGPU][Waitcnt] fix "comparison of integers of different signs" build error""
( fe0a456510131f268e388c4a18a92f575c0db183 ), which was inadvertantly reverted via
2b2ee080f0164485562593b1b87291a48cea4a9a .

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@337156 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed