cfg80211: remove racy beacon_interval assignment

In case of AP mode, the beacon interval is already reset to
zero inside cfg80211_stop_ap(), and in the other modes it
isn't relevant. Remove the assignment to remove a potential
race since the assignment isn't properly locked.
Reported-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/core.c

@@ -788,8 +788,6 @@ void cfg80211_leave(struct cfg80211_registered_device *rdev,
 	default:
 		break;
 	}
-
-	wdev->beacon_interval = 0;
 }
 
 static int cfg80211_netdev_notifier_call(struct notifier_block *nb,