[llvm] [PGO][SampledInstr] Correct off by 1s and allow 100% sampling (PR #113350)

[via llvm-commits]

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@@ -184,21 +184,48 @@ static cl::opt<unsigned> SampledInstrPeriod(
     cl::desc("Set the profile instrumentation sample period. For each sample "
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xur-llvm wrote:

Please mention 0 is not a valid value.

https://github.com/llvm/llvm-project/pull/113350