[NFC][InstrProf] Increment valid profile stat in populateCoverage (#89660)

We increment `NumOfCSPGOFunc` and `NumOfPGOFunc` in
`PGOUseFunc::readCounters()` already. We should do the same in
`PGOUseFunc::populateCoverage`.


https://github.com/llvm/llvm-project/blob/83bc7b57714dc2f6b33c188f2b95a0025468ba51/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp#L1331