Add compact map display that does not output the whole cpu matrix, only
cpus that got event.

  $ perf sched map --compact
    *A0   1082427.094098 secs A0 => perf:19404 (CPU 2)
     A0 *.    1082427.094127 secs .  => swapper:0 (CPU 1)
     A0  .  *B0   1082427.094174 secs B0 => rcuos/2:25 (CPU 3)
     A0  .  *.    1082427.094177 secs
    *C0  .   .    1082427.094187 secs C0 => migration/2:21
     C0 *A0  .    1082427.094193 secs
    *.   A0  .    1082427.094195 secs
    *D0  A0  .    1082427.094402 secs D0 => rngd:968
    *.   A0  .    1082427.094406 secs
     .  *E0  .    1082427.095221 secs E0 => kworker/1:1:5333
     .   E0 *F0   1082427.095227 secs F0 => xterm:3342

It helps to display sane output for small thread loads on big cpu
servers.
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/1460467771-26532-4-git-send-email-jolsa@kernel.org
[ Add entry in 'perf sched' man page ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>