ath9k: fix max noise floor threshold

Currently the maximum noise floor limit is set as too high (-60dB). The
assumption of having a higher threshold limit is that it would help
de-sensitize the receiver (reduce phy errors) from continuous
interference. But when we have a bursty interference where there are
collisions and then free air time and if the receiver is desensitized too
much, it will miss the normal packets too. Lets make use of chips
specific min, nom and max limits always. This patch helps to improve the
connection stability in congested networks.

Cc: stable@vger.kernel.org
Cc: Paul Stewart <pstew@google.com>
Tested-by: NGary Morain <gmorain@google.com>
Signed-off-by: NMadhan Jaganathan <madhanj@qca.qualcomm.com>
Signed-off-by: NRajkumar Manoharan <rmanohar@qca.qualcomm.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

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

@@ -20,7 +20,6 @@
 
 /* Common calibration code */
 
-#define ATH9K_NF_TOO_HIGH	-60
 
 static int16_t ath9k_hw_get_nf_hist_mid(int16_t *nfCalBuffer)
 {
@@ -346,10 +345,10 @@ static void ath9k_hw_nf_sanitize(struct ath_hw *ah, s16 *nf)
 			"NF calibrated [%s] [chain %d] is %d\n",
 			(i >= 3 ? "ext" : "ctl"), i % 3, nf[i]);
 
-		if (nf[i] > ATH9K_NF_TOO_HIGH) {
+		if (nf[i] > limit->max) {
 			ath_dbg(common, CALIBRATE,
 				"NF[%d] (%d) > MAX (%d), correcting to MAX\n",
-				i, nf[i], ATH9K_NF_TOO_HIGH);
+				i, nf[i], limit->max);
 			nf[i] = limit->max;
 		} else if (nf[i] < limit->min) {
 			ath_dbg(common, CALIBRATE,