perf vendor events power8: Branch_prediction, latency, bus_stats,...

perf vendor events power8: Branch_prediction, latency, bus_stats, instruction_mix & instruction_stats metrics

POWER8 metrics are not well publicized.  Some are here:

  https://www.ibm.com/support/knowledgecenter/en/SSFK5S_2.2.0/com.ibm.cluster.pedev.v2r2.pedev100.doc/bl7ug_derivedmetricspower8.htm

This patch is for metric groups:
- branch_prediction
- latency
- bus_stats
- instruction_mix
- instruction_stats_percent_per_ref

Signed-off-by: Paul Clarke <pc@us.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Carl Love <cel@us.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20190207175314.31813-4-pc@us.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>