iwlwifi: mvm: track the number of Rx BA sessions

The firmware / HW can't support more than 16 Rx BA sessions.
Deny any attemps to open more sessions than that.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
diff --git a/drivers/net/wireless/iwlwifi/mvm/mac80211.c b/drivers/net/wireless/iwlwifi/mvm/mac80211.c
index cab2f0c..1a4a032 100644
--- a/drivers/net/wireless/iwlwifi/mvm/mac80211.c
+++ b/drivers/net/wireless/iwlwifi/mvm/mac80211.c
@@ -389,6 +389,7 @@
 	ieee80211_wake_queues(mvm->hw);
 
 	mvm->vif_count = 0;
+	mvm->rx_ba_sessions = 0;
 }
 
 static int iwl_mvm_mac_start(struct ieee80211_hw *hw)