When a device was disconnected the driver may hang at waiting for urbs it never
will get. Fix this by using a timeout while waiting for the used semaphore.

There is still a memory leak if a timeout happens, but at least the driver
now continues his disconnect routine.

...

--- a/drivers/video/udlfb.c
+++ b/drivers/video/udlfb.c

@@ -1832,8 +1832,9 @@ static void dlfb_free_urb_list(struct dlfb_data *dev)
 	/* keep waiting and freeing, until we've got 'em all */
 	while (count--) {
 
-		/* Getting interrupted means a leak, but ok at disconnect */
-		ret = down_interruptible(&dev->urbs.limit_sem);
+		/* Timeout likely occurs at disconnect (resulting in a leak) */
+		ret = down_timeout_killable(&dev->urbs.limit_sem,
+						FREE_URB_TIMEOUT);
 		if (ret)
 			break;