perf record: Combine some auxtrace initialization into a single function

In preparation for adding AUX area sampling support, combine some
auxtrace initialization into a single function.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1520327598-1317-2-git-send-email-adrian.hunter@intel.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>