md: flush md_rdev_misc_wq for HOT_ADD_DISK case

Since rdev->kobj is removed asynchronously, it is possible that the
rdev->kobj still exists when try to add the rdev again after rdev
is removed. But this path md_ioctl (HOT_ADD_DISK) -> hot_add_disk
-> bind_rdev_to_array missed it.
Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

drivers/md/md.c

@@ -7512,7 +7512,7 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
 
 	}
 
-	if (cmd == ADD_NEW_DISK)
+	if (cmd == ADD_NEW_DISK || cmd == HOT_ADD_DISK)
 		flush_rdev_wq(mddev);
 
 	if (cmd == HOT_REMOVE_DISK)