[media] v4l2-async: Use kmalloc_array() in v4l2_async_notifier_unregister()

A multiplication for the size determination of a memory allocation
indicated that an array data structure should be processed.
Thus use the corresponding function "kmalloc_array".

This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/v4l2-core/v4l2-async.c

@@ -202,7 +202,7 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
 	if (!notifier->v4l2_dev)
 		return;
 
-	dev = kmalloc(n_subdev * sizeof(*dev), GFP_KERNEL);
+	dev = kmalloc_array(n_subdev, sizeof(*dev), GFP_KERNEL);
 	if (!dev) {
 		dev_err(notifier->v4l2_dev->dev,
 			"Failed to allocate device cache!\n");