rt2x00: Centralize rt2800 beacon writing.

The beacon writing functions of rt2800pci and rt2800usb are now identical.
Move them to rt2800lib to only have one central function.

Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>

drivers/net/wireless/rt2x00/rt2800lib.h

@@ -114,6 +114,8 @@ void rt2800_mcu_request(struct rt2x00_dev *rt2x00dev,
 void rt2800_write_txwi(__le32 *txwi, struct txentry_desc *txdesc);
 void rt2800_process_rxwi(struct sk_buff *skb, struct rxdone_entry_desc *txdesc);
 
+void rt2800_write_beacon(struct queue_entry *entry, struct txentry_desc *txdesc);
+
 extern const struct rt2x00debug rt2800_rt2x00debug;
 
 int rt2800_rfkill_poll(struct rt2x00_dev *rt2x00dev);