rt2x00: Implement rt2x00usb_kick_tx_queue()

rt2x00usb_kick_tx_queue() will loop over all entries
within the INDEX_DONE->INDEX range and kick each entry
which is pending to be kicked. This makes the kick_tx_queue
approach work the same as with the PCI drivers which
will allow for more code generalisation into rt2x00lib.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rt2x00/rt2x00usb.h b/drivers/net/wireless/rt2x00/rt2x00usb.h
index 26f53f8..460d32c 100644
--- a/drivers/net/wireless/rt2x00/rt2x00usb.h
+++ b/drivers/net/wireless/rt2x00/rt2x00usb.h
@@ -245,6 +245,17 @@
 	struct urb *guardian_urb;
 };
 
+/**
+ * rt2x00usb_kick_tx_queue - Kick data queue
+ * @rt2x00dev: Pointer to &struct rt2x00_dev
+ * @qid: Data queue to kick
+ *
+ * This will walk through all entries of the queue and push all pending
+ * frames to the hardware as a single burst.
+ */
+void rt2x00usb_kick_tx_queue(struct rt2x00_dev *rt2x00dev,
+			     const enum data_queue_qid qid);
+
 /*
  * Device initialization handlers.
  */