ath9k_hw: fix periodic noise floor calibration on AR9003

The periodic noise floor calibration is broken on this chip family, because
it keeps triggering a software-filtered noise floor calibration, but never
reads the result before uploading the history buffer value to the hardware.

Fix this with a call to ath9k_hw_getnf(), just like on AR9002.
Signed-off-by: NFelix Fietkau <nbd@openwrt.org>
Acked-by: NLuis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/ar9003_calib.c

@@ -148,6 +148,12 @@ static bool ar9003_hw_calibrate(struct ath_hw *ah,
 
 	/* Do NF cal only at longer intervals */
 	if (longcal) {
+		/*
+		 * Get the value from the previous NF cal and update
+		 * history buffer.
+		 */
+		ath9k_hw_getnf(ah, chan);
+
 		/*
 		 * Load the NF from history buffer of the current channel.
 		 * NF is slow time-variant, so it is OK to use a historical