[X86] AMD Piledriver (BdVer2): major cleanup (mainly inverse throughput)

I've started this cleanup more several times now, but got sidetracked
elsewhere, e.g. by llvm-exegesis problems. Not this time, finally!

This is mainly cleaning up the inverse throughput values,
and a few latencies/uops, based on the llvm-exegesis measured values.

Though this is not complete by any means,
there's certainly more cleanup to be done.

The performance numbers (i've only checked by RawSpeed benchmark) aren't
really surprising - overall this *slightly* (< -1%) improves perf.

llvm-svn: 360341