rt2x00: move extra_tx_headroom field from rt2x00_ops to rt2x00_dev

The extra_tx_headroom field of struct rt2x00_ops
indicates the extra TX headroom size required for
a given device. This data is redundant, the value
can be computed from the desc_size and winfo_size
fields of the TX queues.

Move the extra_tx_headroom field to struct rt2x00_dev,
compute its value in the probe routine and use the
cached value in the rest of the code.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Acked-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rt2x00/rt2x00dev.c b/drivers/net/wireless/rt2x00/rt2x00dev.c
index dff5012..f03e3bb 100644
--- a/drivers/net/wireless/rt2x00/rt2x00dev.c
+++ b/drivers/net/wireless/rt2x00/rt2x00dev.c
@@ -334,7 +334,7 @@
 	/*
 	 * Remove the extra tx headroom from the skb.
 	 */
-	skb_pull(entry->skb, rt2x00dev->ops->extra_tx_headroom);
+	skb_pull(entry->skb, rt2x00dev->extra_tx_headroom);
 
 	/*
 	 * Signal that the TX descriptor is no longer in the skb.
@@ -1049,7 +1049,7 @@
 	 */
 	rt2x00dev->hw->extra_tx_headroom =
 		max_t(unsigned int, IEEE80211_TX_STATUS_HEADROOM,
-		      rt2x00dev->ops->extra_tx_headroom);
+		      rt2x00dev->extra_tx_headroom);
 
 	/*
 	 * Take TX headroom required for alignment into account.
@@ -1256,6 +1256,17 @@
 	rt2x00dev->hw->wiphy->n_iface_combinations = 1;
 }
 
+static unsigned int rt2x00dev_extra_tx_headroom(struct rt2x00_dev *rt2x00dev)
+{
+	if (WARN_ON(!rt2x00dev->tx))
+		return 0;
+
+	if (rt2x00_is_usb(rt2x00dev))
+		return rt2x00dev->tx[0].winfo_size + rt2x00dev->tx[0].desc_size;
+
+	return rt2x00dev->tx[0].winfo_size;
+}
+
 /*
  * driver allocation handlers.
  */
@@ -1330,6 +1341,9 @@
 	if (retval)
 		goto exit;
 
+	/* Cache TX headroom value */
+	rt2x00dev->extra_tx_headroom = rt2x00dev_extra_tx_headroom(rt2x00dev);
+
 	/*
 	 * Determine which operating modes are supported, all modes
 	 * which require beaconing, depend on the availability of