rt2x00: rt2800usb: use rt2x00dev->rx->limit

The RX data queue is initialized already when
the rt2800_usb_enable_radio() 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->rx->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/rt2800usb.c

@@ -327,7 +327,7 @@ static int rt2800usb_enable_radio(struct rt2x00_dev *rt2x00dev)
 	 * this limit so reduce the number to prevent errors.
 	 */
 	rt2x00_set_field32(&reg, USB_DMA_CFG_RX_BULK_AGG_LIMIT,
-			   ((rt2x00dev->ops->rx->entry_num * DATA_FRAME_SIZE)
+			   ((rt2x00dev->rx->limit * DATA_FRAME_SIZE)
 			    / 1024) - 3);
 	rt2x00_set_field32(&reg, USB_DMA_CFG_RX_BULK_EN, 1);
 	rt2x00_set_field32(&reg, USB_DMA_CFG_TX_BULK_EN, 1);