perf ftrace: Add 'tail' option to --graph-opts

The 'graph-tail' option is to print function name as a comment at the end.
This is useful when a large function is mixed with other functions
(possibly from different CPUs).

For example,

  $ sudo perf ftrace -- perf stat true
  ...
   1)               |    get_unused_fd_flags() {
   1)               |      alloc_fd() {
   1)   0.178 us    |        _raw_spin_lock();
   1)   0.187 us    |        expand_files();
   1)   0.169 us    |        _raw_spin_unlock();
   1)   1.211 us    |      }
   1)   1.503 us    |    }

  $ sudo perf ftrace --graph-opts tail -- perf stat true
  ...
   1)               |    get_unused_fd_flags() {
   1)               |      alloc_fd() {
   1)   0.099 us    |        _raw_spin_lock();
   1)   0.083 us    |        expand_files();
   1)   0.081 us    |        _raw_spin_unlock();
   1)   0.601 us    |      } /* alloc_fd */
   1)   0.751 us    |    } /* get_unused_fd_flags */

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Changbin Du <changbin.du@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lore.kernel.org/lkml/20240729004127.238611-2-namhyung@kernel.org


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