farsync: fix support for over 30 cards

We're trying to fill a 64 bit bitmap but only the lower 30 shifts work
because the shift wraps around.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wan/farsync.c

@@ -597,7 +597,7 @@ fst_q_work_item(u64 * queue, int card_index)
 	 * bottom half for the card.  Note the limitation of 64 cards.
 	 * That ought to be enough
 	 */
-	mask = 1 << card_index;
+	mask = (u64)1 << card_index;
 	*queue |= mask;
 	spin_unlock_irqrestore(&fst_work_q_lock, flags);
 }