at76c50x-usb: use ether_addr_equal_64bits

Ether_addr_equal_64bits is more efficient than ether_addr_equal, and can be
used when each argument is an array within a structure that contains at
least two bytes of data beyond the array.

The structures involved are:
at76_priv defined in drivers/net/wireless/at76c50x-usb.h and
ieee80211_mgmt defined in include/linux/ieee80211.h

This was done using Coccinelle (http://coccinelle.lip6.fr/).
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/at76c50x-usb.c

@@ -1721,7 +1721,7 @@ static void at76_mac80211_tx(struct ieee80211_hw *hw,
 	 * following workaround is necessary. If the TX frame is an
 	 * authentication frame extract the bssid and send the CMD_JOIN. */
 	if (mgmt->frame_control & cpu_to_le16(IEEE80211_STYPE_AUTH)) {
-		if (!ether_addr_equal(priv->bssid, mgmt->bssid)) {
+		if (!ether_addr_equal_64bits(priv->bssid, mgmt->bssid)) {
 			memcpy(priv->bssid, mgmt->bssid, ETH_ALEN);
 			ieee80211_queue_work(hw, &priv->work_join_bssid);
 			dev_kfree_skb_any(skb);