staging: most: hdm-usb: Remove invalid reference error

commit e3479f77("staging: most: hdm-usb: Remove create_workqueue()")
cancel_work_sync(&anchor->clear_work_obj) is introduced after freeing
`anchor` causing a invalid reference error. This patch removes this
error by shifting the call to cancel_work_sync before freeing
`anchor`.

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/most/hdm-usb/hdm_usb.c

@@ -221,11 +221,10 @@ static void free_anchored_buffers(struct most_dev *mdev, unsigned int channel)
 		}
 		spin_lock_irqsave(&mdev->anchor_list_lock[channel], flags);
 		list_del(&anchor->list);
+		cancel_work_sync(&anchor->clear_work_obj);
 		kfree(anchor);
 	}
 	spin_unlock_irqrestore(&mdev->anchor_list_lock[channel], flags);
-
-	cancel_work_sync(&anchor->clear_work_obj);
 }
 
 /**