perf/x86/amd: Enable northbridge performance counters on AMD family 15h

On AMD family 15h processors, there are 4 new performance
counters (in addition to 6 core performance counters) that can
be used for counting northbridge events (i.e. DRAM accesses).

Their bit fields are almost identical to the core performance
counters. However, unlike the core performance counters, these
MSRs are shared between multiple cores (that share the same
northbridge).

We will reuse the same code path as existing family 10h
northbridge event constraints handler logic to enforce
this sharing.

Signed-off-by: Jacob Shin <jacob.shin@amd.com>
Acked-by: Stephane Eranian <eranian@google.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Jacob Shin <jacob.shin@amd.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1360171589-6381-7-git-send-email-jacob.shin@amd.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>