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/trace.h b/net/mac80211/trace.h
index 02ac535..38fae7e 100644
--- a/net/mac80211/trace.h
+++ b/net/mac80211/trace.h
@@ -672,13 +672,13 @@
 );
 
 TRACE_EVENT(drv_set_coverage_class,
-	TP_PROTO(struct ieee80211_local *local, u8 value),
+	TP_PROTO(struct ieee80211_local *local, s16 value),
 
 	TP_ARGS(local, value),
 
 	TP_STRUCT__entry(
 		LOCAL_ENTRY
-		__field(u8, value)
+		__field(s16, value)
 	),
 
 	TP_fast_assign(