perf sched timehist: Add --state option

The --state option is to show task state when switched out.  The state
is printed as a single character like in the /proc but I added 'I' for
idle state rather than 'R'.

  $ perf sched timehist --state | head
  Samples do not have callchains.
      time cpu task name              wait time sch delay run time state
               [tid/pid]                 (msec)    (msec)   (msec)
  -------- --- ----------------------- -------- ------------------ -----
  1.753791 [3] <idle>                     0.000     0.000    0.000     I
  1.753834 [1] perf[27469]                0.000     0.000    0.000     S
  1.753904 [3] perf[27470]                0.000     0.006    0.112     S
  1.753914 [1] <idle>                     0.000     0.000    0.079     I
  1.753915 [3] migration/3[23]            0.000     0.002    0.011     S
  1.754287 [2] <idle>                     0.000     0.000    0.000     I
  1.754335 [2] transmission[1773/1739]    0.000     0.004    0.047     S

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170113104523.31212-2-namhyung@kernel.org


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