module: Update prototype for ref_module (formerly use_module)

Commit 9bea7f23 renamed use_module to
ref_module (and changed its return value), but forgot to update this
prototype in module.h.
Signed-off-by: Anders Kaseorg <andersk@ksplice.com>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

include/linux/module.h

@@ -517,7 +517,7 @@ static inline void __module_get(struct module *module)
 #define symbol_put_addr(p) do { } while(0)
 
 #endif /* CONFIG_MODULE_UNLOAD */
-int use_module(struct module *a, struct module *b);
+int ref_module(struct module *a, struct module *b);
 
 /* This is a #define so the string doesn't get put in every .o file */
 #define module_name(mod)			\