s390/cio: use DECLARE_WAIT_QUEUE_HEAD() for wait_queue

wait_queue_head_t can be initialized automatically with
DECLARE_WAIT_QUEUE_HEAD() rather than explicitly calling
init_waitqueue_head().
Signed-off-by: Shixin Liu <liushixin2@huawei.com>
Acked-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

drivers/s390/cio/css.c

@@ -652,13 +652,12 @@ static void css_sch_todo(struct work_struct *work)
 
 static struct idset *slow_subchannel_set;
 static DEFINE_SPINLOCK(slow_subchannel_lock);
-static wait_queue_head_t css_eval_wq;
+static DECLARE_WAIT_QUEUE_HEAD(css_eval_wq);
 static atomic_t css_eval_scheduled;
 
 static int __init slow_subchannel_init(void)
 {
 	atomic_set(&css_eval_scheduled, 0);
-	init_waitqueue_head(&css_eval_wq);
 	slow_subchannel_set = idset_sch_new();
 	if (!slow_subchannel_set) {
 		CIO_MSG_EVENT(0, "could not allocate slow subchannel set\n");