perf sched timehist: Add -V/--cpu-visual option

perf sched timehist: Add -V/--cpu-visual option

The -V option provides a visual aid for sched switches by cpu:

  $ perf sched timehist -V
             time    cpu  0123456789abc  task name              b/n time  sch delay   run time
                                         [tid/pid]                (msec)     (msec)     (msec)
  --------------- ------  -------------  --------------------  ---------  ---------  ---------
  ...
   2412598.429696 [0009]           i     <idle>                    0.000      0.000      0.000
   2412598.429767 [0002]    s            perf[7219]                0.000      0.000      0.000
   2412598.429783 [0009]           s     perf[7220]                0.000      0.006      0.087
   2412598.429794 [0010]            i    <idle>                    0.000      0.000      0.000
   2412598.429795 [0009]           s     migration/9[53]           0.000      0.003      0.011
   2412598.430370 [0010]            s    sleep[7220]               0.011      0.000      0.576
   2412598.432584 [0003]     i           <idle>                    0.000      0.000      0.000
  ...

Committer notes:

'i' marks idle time, 's' are scheduler events.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/20161116060634.28477-8-namhyung@kernel.org
[ Add documentation based on above commit message ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>