Input: serio - mark serio_register_driver() __must_check

Also remove extra declaration of serio_register_driver().
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

include/linux/serio.h

@@ -87,11 +87,10 @@ void serio_unregister_port(struct serio *serio);
 void serio_unregister_child_port(struct serio *serio);
 
 int __serio_register_driver(struct serio_driver *drv, struct module *owner, const char *mod_name);
-static inline int serio_register_driver(struct serio_driver *drv)
+static inline int __must_check serio_register_driver(struct serio_driver *drv)
 {
 	return __serio_register_driver(drv, THIS_MODULE, KBUILD_MODNAME);
 }
-int serio_register_driver(struct serio_driver *drv);
 void serio_unregister_driver(struct serio_driver *drv);
 
 static inline int serio_write(struct serio *serio, unsigned char data)