Introduce the perf_event__synthesize_cpu_map function to synthesize a
struct cpu_map.

Added generic interface:
  cpu_map_data__alloc
  cpu_map_data__synthesize

to make the cpu_map synthesizing usable for other events.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Tested-by: NKan Liang <kan.liang@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1445784728-21732-9-git-send-email-jolsa@kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>