rt2x00: Implement tx power temperature compensation

rt2800 devices should adjust their tx power in accordance with the
eeproms temperature calibration values. Add a new driver callback
gain_calibration that is called every 4 seconds.

The rt2800 gain calibration routine simply runs the tx power
configuration that takes care of calculating the temperature
compensation delta.

We don't need to synchronize the calls to rt2800_config_txpower
as they should all happen from mac80211's single threaded workqueue.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00.h

@@ -348,6 +348,11 @@ struct link {
 	 * to bring the device/driver back into the desired state.
 	 */
 	struct delayed_work watchdog_work;
+
+	/*
+	 * Work structure for scheduling periodic AGC adjustments.
+	 */
+	struct delayed_work agc_work;
 };
 
 enum rt2x00_delayed_flags {
@@ -556,6 +561,7 @@ struct rt2x00lib_ops {
 			     struct link_qual *qual);
 	void (*link_tuner) (struct rt2x00_dev *rt2x00dev,
 			    struct link_qual *qual, const u32 count);
+	void (*gain_calibration) (struct rt2x00_dev *rt2x00dev);
 
 	/*
 	 * Data queue handlers.