proc: use WARN() rather than printk+backtrace

Use WARN() rather than a printk() + backtrace();
this gives a more standard format message as well as complete
information (including line numbers etc) that will be collected
by kerneloops.org
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>

fs/proc/generic.c

@@ -547,9 +547,8 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp
 
 	for (tmp = dir->subdir; tmp; tmp = tmp->next)
 		if (strcmp(tmp->name, dp->name) == 0) {
-			printk(KERN_WARNING "proc_dir_entry '%s/%s' already registered\n",
+			WARN(1, KERN_WARNING "proc_dir_entry '%s/%s' already registered\n",
 				dir->name, dp->name);
-			dump_stack();
 			break;
 		}