mac80211: extend set_coverage_class signature

Extend mac80211 set_coverage_class API in order to enable ACK timeout
estimation algorithm (dynack) passing coverage class equals to -1
to lower drivers. Synchronize set_coverage_class routine signature with
mac80211 function pointer for p54, ath9k, ath9k_htc and ath5k drivers.

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 4c1681b..101ae6c 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1978,8 +1978,13 @@
 			return err;
 	}
 
-	if (changed & WIPHY_PARAM_COVERAGE_CLASS) {
-		err = drv_set_coverage_class(local, wiphy->coverage_class);
+	if ((changed & WIPHY_PARAM_COVERAGE_CLASS) ||
+	    (changed & WIPHY_PARAM_DYN_ACK)) {
+		s16 coverage_class;
+
+		coverage_class = changed & WIPHY_PARAM_COVERAGE_CLASS ?
+					wiphy->coverage_class : -1;
+		err = drv_set_coverage_class(local, coverage_class);
 
 		if (err)
 			return err;