ath6kl: silence "invalid rate" warning

For some reason firmware is sending invalid rates when we try to
query current bitrate from ath6kl_get_station() and a warning is issued:

[ 3810.415720] ath6kl: invalid rate: 1935633515
[ 3811.105493] ath6kl: invalid rate: 1935633515
[ 3811.556063] ath6kl: invalid rate: 1935633515

As the warning happens way too often, convert the warning to a debug
message once we have a proper fix. But to make it easy to follow
how often the problem appears, add a debugfs to print
various statistics about workarounds and make this issue the first WAR.

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
diff --git a/drivers/net/wireless/ath/ath6kl/cfg80211.c b/drivers/net/wireless/ath/ath6kl/cfg80211.c
index c84f53d6..8d9fbd4 100644
--- a/drivers/net/wireless/ath/ath6kl/cfg80211.c
+++ b/drivers/net/wireless/ath/ath6kl/cfg80211.c
@@ -1365,7 +1365,9 @@
 		sinfo->txrate.flags |= RATE_INFO_FLAGS_40_MHZ_WIDTH;
 		sinfo->txrate.flags |= RATE_INFO_FLAGS_MCS;
 	} else {
-		ath6kl_warn("invalid rate: %d\n", rate);
+		ath6kl_dbg(ATH6KL_DBG_WLAN_CFG,
+			   "invalid rate from stats: %d\n", rate);
+		ath6kl_debug_war(ar, ATH6KL_WAR_INVALID_RATE);
 		return 0;
 	}