[X86] AMD Piledriver (BdVer2): fine-tune some latencies

Based on llvm-exegesis measurements.

Now that llvm-exegesis is ~2 magnitudes faster, and is a bit smarter,
it is now possible to continue cleanup of the scheduler model.

With this, there are no more latency inconsistencies for the
opcodes that produce stable measurements, and only a few inconsistencies
for unstable measurements (MMX_* opcodes, opcodes that llvm-exegesis
measures by chaining - CMP, TEST, BT, SETcc, CVT, MOV, etc.)

llvm-svn: 357169