can: only call can_stat_update with procfs

The change to leave out procfs support in CAN when CONFIG_PROC_FS
is not set was incomplete and leads to a build error:

net/built-in.o: In function `can_init':
:(.init.text+0x9858): undefined reference to `can_stat_update'
ERROR: "can_stat_update" [net/can/can.ko] undefined!

This tries a better approach, encapsulating all of the calls
within IS_ENABLED(), so we also leave out the timer function
from the object file.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Fixes: a20fadf8 ("can: build proc support only if CONFIG_PROC_FS is activated")
Signed-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>

net/can/af_can.c

@@ -911,14 +911,14 @@ static __init int can_init(void)
 	if (!rcv_cache)
 		return -ENOMEM;
 
+	if (IS_ENABLED(CONFIG_PROC_FS)) {
 		if (stats_timer) {
 		/* the statistics are updated every second (timer triggered) */
 			setup_timer(&can_stattimer, can_stat_update, 0);
 			mod_timer(&can_stattimer, round_jiffies(jiffies + HZ));
-	} else
-		can_stattimer.function = NULL;
-
+		}
 		can_init_proc();
+	}
 
 	/* protocol register */
 	sock_register(&can_family_ops);
@@ -933,10 +933,12 @@ static __exit void can_exit(void)
 {
 	struct net_device *dev;
 
+	if (IS_ENABLED(CONFIG_PROC_FS)) {
 		if (stats_timer)
 			del_timer_sync(&can_stattimer);
 
 		can_remove_proc();
+	}
 
 	/* protocol unregister */
 	dev_remove_pack(&canfd_packet);

net/can/af_can.h

@@ -113,19 +113,8 @@ struct s_pstats {
 extern struct dev_rcv_lists can_rx_alldev_list;
 
 /* function prototypes for the CAN networklayer procfs (proc.c) */
-#ifdef CONFIG_PROC_FS
 void can_init_proc(void);
 void can_remove_proc(void);
-#else
-static inline void can_init_proc(void)
-{
-	pr_info("can: Can't create /proc/net/can. CONFIG_PROC_FS missing!\n");
-}
-
-static inline void can_remove_proc(void)
-{
-}
-#endif
 void can_stat_update(unsigned long data);
 
 /* structures and variables from af_can.c needed in proc.c for reading */