Driver core: fixed add_bind_files() definition

When CONFIG_HOTPLUG is n, add_bind_files() definition is wrong.
This patch has fixed it.
Signed-off-by: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/base/bus.c

@@ -467,7 +467,7 @@ static void remove_bind_files(struct device_driver *drv)
 	driver_remove_file(drv, &driver_attr_unbind);
 }
 #else
-static inline void add_bind_files(struct device_driver *drv) {}
+static inline int add_bind_files(struct device_driver *drv) { return 0; }
 static inline void remove_bind_files(struct device_driver *drv) {}
 #endif