can: build proc support only if CONFIG_PROC_FS is activated

When building can subsystem with CONFIG_PROC_FS=n I detected some unused
variables warning by using proc functions. In CAN the proc handling is
nicely placed in one object file. This patch adds simple add a
dependency on CONFIG_PROC_FS for CAN's proc.o file and corresponding
static inline no-op functions.

Signed-off-by: Alexander Aring <[e-mail]>
Acked-by: Oliver Hartkopp <[e-mail]>
[mkl: provide static inline noops instead of using #ifdefs]
Signed-off-by: Marc Kleine-Budde <[e-mail]>

net/can/Makefile

···
 #
 
 obj-$(CONFIG_CAN)	+= can.o
-can-y			:= af_can.o proc.o
+can-y			:= af_can.o
+can-$(CONFIG_PROC_FS)	+= proc.o
 
 obj-$(CONFIG_CAN_RAW)	+= can-raw.o
 can-raw-y		:= raw.o

net/can/af_can.h

···
 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 */

net/can/proc.c

···
 	can_dir = proc_mkdir("can", init_net.proc_net);
 
 	if (!can_dir) {
-		printk(KERN_INFO "can: failed to create /proc/net/can . "
-		       "CONFIG_PROC_FS missing?\n");
+		pr_info("can: failed to create /proc/net/can.\n");
 		return;
 	}