locking/ww_mutex/test: Use swap() macro

Fixes the following Coccinelle/coccicheck warning reported by
swap.cocci:

  WARNING opportunity for swap()

Compile-tested only.

[Boqun: Add the report tags from Jiapeng and Abaci Robot [1].]

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Reported-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=11531
Link: https://lore.kernel.org/r/20241025081455.55089-1-jiapeng.chong@linux.alibaba.com [1]
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20240731135850.81018-2-thorsten.blum@toblux.com

kernel/locking/test-ww_mutex.c

@@ -404,7 +404,7 @@ static inline u32 prandom_u32_below(u32 ceil)
 static int *get_random_order(int count)
 {
 	int *order;
-	int n, r, tmp;
+	int n, r;
 
 	order = kmalloc_array(count, sizeof(*order), GFP_KERNEL);
 	if (!order)
@@ -415,11 +415,8 @@ static int *get_random_order(int count)
 
 	for (n = count - 1; n > 1; n--) {
 		r = prandom_u32_below(n + 1);
-		if (r != n) {
-			tmp = order[n];
-			order[n] = order[r];
-			order[r] = tmp;
-		}
+		if (r != n)
+			swap(order[n], order[r]);
 	}
 
 	return order;