perf config: Reimplement show_config() using config_set__for_each

Recently config_set__for_each got added.  In order to let show_config()
be short and clear, rewrite this function using it.
Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1466691272-24117-4-git-send-email-treeze.taeung@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-config.c

@@ -37,23 +37,16 @@ static int show_config(struct perf_config_set *set)
 {
 	struct perf_config_section *section;
 	struct perf_config_item *item;
-	struct list_head *sections;
 
 	if (set == NULL)
 		return -1;
 
-	sections = &set->sections;
-	if (list_empty(sections))
-		return -1;
-
-	list_for_each_entry(section, sections, node) {
-		list_for_each_entry(item, &section->items, node) {
-			char *value = item->value;
+	perf_config_set__for_each_entry(set, section, item) {
+		char *value = item->value;
 
-			if (value)
-				printf("%s.%s=%s\n", section->name,
-				       item->name, value);
-		}
+		if (value)
+			printf("%s.%s=%s\n", section->name,
+			       item->name, value);
 	}
 
 	return 0;