rt2800: radio 3xxx: add channel switch calibration routines

Synchronize code with Ralink driver:
2011_0719_RT3070_RT3370_RT5370_RT5372_Linux_STA_V2.5.0.3_DPO
Based on functions:
RT33xx_ChipSwitchChannel
RT30xx_ChipSwitchChannel
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2800lib.c

@@ -1699,6 +1699,13 @@ static void rt2800_config_channel_rf3xxx(struct rt2x00_dev *rt2x00dev,
 	}
 	rt2800_rfcsr_write(rt2x00dev, 1, rfcsr);
 
+	rt2800_rfcsr_read(rt2x00dev, 30, &rfcsr);
+	rt2x00_set_field8(&rfcsr, RFCSR30_RF_CALIBRATION, 1);
+	rt2800_rfcsr_write(rt2x00dev, 30, rfcsr);
+	msleep(1);
+	rt2x00_set_field8(&rfcsr, RFCSR30_RF_CALIBRATION, 0);
+	rt2800_rfcsr_write(rt2x00dev, 30, rfcsr);
+
 	rt2800_rfcsr_read(rt2x00dev, 23, &rfcsr);
 	rt2x00_set_field8(&rfcsr, RFCSR23_FREQ_OFFSET, rt2x00dev->freq_offset);
 	rt2800_rfcsr_write(rt2x00dev, 23, rfcsr);
@@ -1709,6 +1716,13 @@ static void rt2800_config_channel_rf3xxx(struct rt2x00_dev *rt2x00dev,
 	rt2800_rfcsr_read(rt2x00dev, 7, &rfcsr);
 	rt2x00_set_field8(&rfcsr, RFCSR7_RF_TUNING, 1);
 	rt2800_rfcsr_write(rt2x00dev, 7, rfcsr);
+
+	rt2800_rfcsr_read(rt2x00dev, 30, &rfcsr);
+	rt2x00_set_field8(&rfcsr, RFCSR30_RF_CALIBRATION, 1);
+	rt2800_rfcsr_write(rt2x00dev, 30, rfcsr);
+	msleep(1);
+	rt2x00_set_field8(&rfcsr, RFCSR30_RF_CALIBRATION, 0);
+	rt2800_rfcsr_write(rt2x00dev, 30, rfcsr);
 }
 
 static void rt2800_config_channel_rf3052(struct rt2x00_dev *rt2x00dev,