block: let elv_register() return void

elv_register() always returns 0, and there isn't anything it does where
it should return an error (the only error condition is so grave that
it's handled with a BUG_ON).

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/deadline-iosched.c

@@ -467,7 +467,9 @@ static struct elevator_type iosched_deadline = {
 
 static int __init deadline_init(void)
 {
-	return elv_register(&iosched_deadline);
+	elv_register(&iosched_deadline);
+
+	return 0;
 }
 
 static void __exit deadline_exit(void)