connector: fix defined but not used warning

Fix a build warning in connector.c when CONFIG_PROC_FS is not enabled
by marking the unused function as __maybe_unused.

../drivers/connector/connector.c:242:12: warning: 'cn_proc_show' defined but not used [-Wunused-function]

Signed-off-by: Randy Dunlap <[e-mail]>
Cc: Evgeniy Polyakov <[e-mail]>
Cc: [e-mail]
Signed-off-by: David S. Miller <[e-mail]>

drivers/connector/connector.c

···
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
+#include <linux/compiler.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/list.h>
···
 }
 EXPORT_SYMBOL_GPL(cn_del_callback);
 
-static int cn_proc_show(struct seq_file *m, void *v)
+static int __maybe_unused cn_proc_show(struct seq_file *m, void *v)
 {
 	struct cn_queue_dev *dev = cdev.cbdev;
 	struct cn_callback_entry *cbq;