async: simplify lowest_in_progress()

The code in lowest_in_progress() are duplicated in two branches,
simplify them.

tj: Minor indentation adjustment.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>

kernel/async.c

@@ -84,24 +84,20 @@ static atomic_t entry_count;
 
 static async_cookie_t lowest_in_progress(struct async_domain *domain)
 {
-	struct async_entry *first = NULL;
+	struct list_head *pending;
 	async_cookie_t ret = ASYNC_COOKIE_MAX;
 	unsigned long flags;
 
 	spin_lock_irqsave(&async_lock, flags);
 
-	if (domain) {
-		if (!list_empty(&domain->pending))
-			first = list_first_entry(&domain->pending,
-					struct async_entry, domain_list);
-	} else {
-		if (!list_empty(&async_global_pending))
-			first = list_first_entry(&async_global_pending,
-					struct async_entry, global_list);
-	}
+	if (domain)
+		pending = &domain->pending;
+	else
+		pending = &async_global_pending;
 
-	if (first)
-		ret = first->cookie;
+	if (!list_empty(pending))
+		ret = list_first_entry(pending, struct async_entry,
+				       domain_list)->cookie;
 
 	spin_unlock_irqrestore(&async_lock, flags);
 	return ret;