Allow user to limit output to one or more CPUs. Really helpful on
systems with a large number of cpus.

Committer testing:

  # perf sched record -a sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 1.765 MB perf.data (1412 samples) ]
  [root@quaco ~]# perf sched timehist | head
  Samples do not have callchains.
             time    cpu  task name                       wait time  sch delay   run time
                          [tid/pid]                          (msec)     (msec)     (msec)
  --------------- ------  ------------------------------  ---------  ---------  ---------
     66307.802686 [0000]  perf[13086]                         0.000      0.000      0.000
     66307.802700 [0000]  migration/0[12]                     0.000      0.001      0.014
     66307.802766 [0001]  perf[13086]                         0.000      0.000      0.000
     66307.802774 [0001]  migration/1[15]                     0.000      0.001      0.007
     66307.802841 [0002]  perf[13086]                         0.000      0.000      0.000
     66307.802849 [0002]  migration/2[20]                     0.000      0.001      0.008
     66307.802913 [0003]  perf[13086]                         0.000      0.000      0.000
  #
  # perf sched timehist --cpu 2 | head
  Samples do not have callchains.
             time    cpu  task name                       wait time  sch delay   run time
                          [tid/pid]                          (msec)     (msec)     (msec)
  --------------- ------  ------------------------------  ---------  ---------  ---------
     66307.802841 [0002]  perf[13086]                         0.000      0.000      0.000
     66307.802849 [0002]  migration/2[20]                     0.000      0.001      0.008
     66307.964485 [0002]  <idle>                              0.000      0.000    161.635
     66307.964811 [0002]  CPU 0/KVM[3589/3561]                0.000      0.056      0.325
     66307.965477 [0002]  <idle>                              0.325      0.000      0.666
     66307.965553 [0002]  CPU 0/KVM[3589/3561]                0.666      0.024      0.076
     66307.966456 [0002]  <idle>                              0.076      0.000      0.903
  #
Signed-off-by: David Ahern <dsahern@gmail.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/20191204173925.66976-1-dsahern@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>