perf stat report: Process event update events

Adding processing of event update events, so perf stat report can store
additional info for events - unit,scale,name.

Committer note:

Before:

  # perf stat record -e power/energy-cores/ -a
  ^C
  Performance counter stats for 'system wide':

             77.41 Joules power/energy-cores/

       1.597176695 seconds time elapsed

  # perf stat report

  Performance counter stats for '/home/acme/bin/perf stat record -e power/energy-cores/ -a':

   332,488,114,176      power/energy-cores/

       1.597176695 seconds time elapsed

  #

After, using the same perf.data file generated in the "Before" case
above:

  # perf stat report

  Performance counter stats for '/home/acme/bin/perf stat record -e power/energy-cores/ -a':

             77.41 Joules power/energy-cores/

       1.597176695 seconds time elapsed

  #

Reported-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.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/1446734469-11352-17-git-send-email-jolsa@kernel.org


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