perf hists: Introduce perf_hpp_list__init function

Introducing perf_hpp_list__init function to have an easy way to
initialize perf_hpp_list struct.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
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/1453109064-1026-16-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/hist.c

@@ -1642,3 +1642,9 @@ int hists__init(void)
 
 	return err;
 }
+
+void perf_hpp_list__init(struct perf_hpp_list *list)
+{
+	INIT_LIST_HEAD(&list->fields);
+	INIT_LIST_HEAD(&list->sorts);
+}

tools/perf/util/hist.h

@@ -386,4 +386,6 @@ int parse_filter_percentage(const struct option *opt __maybe_unused,
 			    const char *arg, int unset __maybe_unused);
 int perf_hist_config(const char *var, const char *value);
 
+void perf_hpp_list__init(struct perf_hpp_list *list);
+
 #endif	/* __PERF_HIST_H */