AMDGPU/InsertWaitcnt: Consistently use uint32_t for scores / time points
AMDGPU/InsertWaitcnt: Consistently use uint32_t for scores / time points

Summary:
There is one obsolete reference to using -1 as an indication of "unknown",
but this isn't actually used anywhere.

Using unsigned makes robust wrapping checks easier.

Reviewers: msearles, rampitec, scott.linder, kanarayan

Subscribers: arsenm, kzhuravl, jvesely, wdng, yaxunl, dstuttard, llvm-commits, tpr, t-tye, hakzsam

Differential Revision: https://reviews.llvm.org/D54230

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@347852 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm