rt2x00: rt61pci: use rt2x00dev->tx->limit

The TX data queue is initialized already when
the rt61pci_txdone() function is called.

Fetch the number of the queue entries from that
instead of using the entry_num field of the data
queue descriptor.

The two values are the same, and the use of the
rt2x00dev->tx->limit value allows us to get rid
of a superfluous pointer dereference.
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt61pci.c

@@ -2175,7 +2175,7 @@ static void rt61pci_txdone(struct rt2x00_dev *rt2x00dev)
 	 * that the TX_STA_FIFO stack has a size of 16. We stick to our
 	 * tx ring size for now.
 	 */
-	for (i = 0; i < rt2x00dev->ops->tx->entry_num; i++) {
+	for (i = 0; i < rt2x00dev->tx->limit; i++) {
 		rt2x00mmio_register_read(rt2x00dev, STA_CSR4, &reg);
 		if (!rt2x00_get_field32(reg, STA_CSR4_VALID))
 			break;