rt2x00: Use saved BBP 25 and 26 values when configuring channel on RT3572.

This brings the rt2800 channel switching code for RT3572 closer to the
v2.5.0.0 Ralink RT3572 driver.
Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2800.h

@@ -2444,6 +2444,8 @@ struct mac_iveiv_entry {
 struct rt2800_drv_data {
 	u8 calibration_bw20;
 	u8 calibration_bw40;
+	u8 bbp25;
+	u8 bbp26;
 };
 
 #endif /* RT2800_H */

drivers/net/wireless/rt2x00/rt2800lib.c

@@ -1754,8 +1754,8 @@ static void rt2800_config_channel_rf3052(struct rt2x00_dev *rt2x00dev,
 	u32 reg;
 
 	if (rf->channel <= 14) {
-		rt2800_bbp_write(rt2x00dev, 25, 0x15);
-		rt2800_bbp_write(rt2x00dev, 26, 0x85);
+		rt2800_bbp_write(rt2x00dev, 25, drv_data->bbp25);
+		rt2800_bbp_write(rt2x00dev, 26, drv_data->bbp26);
 	} else {
 		rt2800_bbp_write(rt2x00dev, 25, 0x09);
 		rt2800_bbp_write(rt2x00dev, 26, 0xff);
@@ -3623,6 +3623,12 @@ static int rt2800_init_rfcsr(struct rt2x00_dev *rt2x00dev)
 			rt2800_init_rx_filter(rt2x00dev, true, 0x27, 0x15);
 	}
 
+	/*
+	 * Save BBP 25 & 26 values for later use in channel switching
+	 */
+	rt2800_bbp_read(rt2x00dev, 25, &drv_data->bbp25);
+	rt2800_bbp_read(rt2x00dev, 26, &drv_data->bbp26);
+
 	if (!rt2x00_rt(rt2x00dev, RT5390)) {
 		/*
 		 * Set back to initial state