[gnome-applets/wip/muktupavels/werror] netspeed: fix -Wmissing-prototypes warning

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 8b5ae357b78d15e3db8bcdddd81da0046c1dd1ba
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sat Apr 4 21:32:36 2020 +0300

    netspeed: fix -Wmissing-prototypes warning

 gnome-applets/netspeed/preferences.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gnome-applets/netspeed/preferences.c b/gnome-applets/netspeed/preferences.c
index 404da8f01..b7ed6fbb7 100644
--- a/gnome-applets/netspeed/preferences.c
+++ b/gnome-applets/netspeed/preferences.c
@@ -145,7 +145,7 @@ free_devices (gpointer data)
   g_list_free_full (data, g_free);
 }
 
-GtkWidget *
+static GtkWidget *
 create_network_hbox (NetspeedPreferences *preferences)
 {
   GtkWidget *network_device_hbox;