rt2x00: Reverse calling order of bus write_tx_desc and driver write_tx_desc.

For rt2800 reverse the calling order of rt2x00pci_write_data and
rt2800pci_write_data. Currently rt2800pci_write_data calls rt2x00pci_write_data
as there can be only 1 driver callback function specified by the driver.
Reverse this calling order by introducing a new driver callback function,
called write_tx_datadesc, which is called from the bus-specific write_tx_data
functions.
Preparation for futher cleanups in the skb data handling of rt2x00.

Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
diff --git a/drivers/net/wireless/rt2x00/rt2x00.h b/drivers/net/wireless/rt2x00/rt2x00.h
index c8e5fed..811844b 100644
--- a/drivers/net/wireless/rt2x00/rt2x00.h
+++ b/drivers/net/wireless/rt2x00/rt2x00.h
@@ -552,6 +552,8 @@
 			       struct txentry_desc *txdesc);
 	int (*write_tx_data) (struct queue_entry *entry,
 			      struct txentry_desc *txdesc);
+	void (*write_tx_datadesc) (struct queue_entry *entry,
+				   struct txentry_desc *txdesc);
 	void (*write_beacon) (struct queue_entry *entry,
 			      struct txentry_desc *txdesc);
 	int (*get_tx_data_len) (struct queue_entry *entry);