perf/x86: Move MSR address offset calculation to architecture specific files

Move counter index to MSR address offset calculation to
architecture specific files. This prepares the way for
perf_event_amd to enable counter addresses that are not
contiguous -- for example AMD Family 15h processors have 6 core
performance counters starting at 0xc0010200 and 4 northbridge
performance counters starting at 0xc0010240.

Signed-off-by: Jacob Shin <jacob.shin@amd.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Stephane Eranian <eranian@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1360171589-6381-5-git-send-email-jacob.shin@amd.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>