perf pmu: Extract function to get JSON alias map

perf pmu: Extract function to get JSON alias map

BugLink: https://bugs.launchpad.net/bugs/1747523
Extract the code to get the per cpu JSON alias into a separate function
for reuse. No behavior changes.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/20170831194036.30146-6-andi@firstfloor.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
(cherry picked from commit d77ade9f4199c77c63e2ae382a8c8fbe0582ede2)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>