itimer: Use printk_once instead of WARN_ONCE

David pointed out, that WARN_ONCE() to report usage of an deprecated
misfeature make folks unhappy. Use printk_once() instead.

Andrew told me to stop grumbling and to remove the silly typecast
while touching the file.

Reported-by: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/itimer.c

@@ -285,9 +285,10 @@ SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 		if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 			return -EFAULT;
 	} else {
-		memset((char *) &set_buffer, 0, sizeof(set_buffer));
-		WARN_ONCE(1, "setitimer: new_value pointer is NULL."
-			  " Misfeature support will be removed\n");
+		memset(&set_buffer, 0, sizeof(set_buffer));
+		printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
+			    " Misfeature support will be removed\n",
+			    current->comm);
 	}
 
 	error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);