perf tools: Enable --children option by default

Now perf top and perf report will show children column by default if
it has callchain information.

Requested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Rodrigo Campos <rodrigo@sdfg.com.ar>
Tested-by: Arun Sharma <asharma@fb.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1401335910-16832-23-git-send-email-namhyung@kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>

tools/perf/util/symbol.c

@@ -33,6 +33,7 @@ struct symbol_conf symbol_conf = {
 	.try_vmlinux_path	= true,
 	.annotate_src		= true,
 	.demangle		= true,
+	.cumulate_callchain	= true,
 	.symfs			= "",
 };