wifi: cfg80211: lock wiphy mutex for rfkill poll

We want to guarantee the mutex is held for pretty much
all operations, so ensure that here as well.

Reported-by: syzbot+7e59a5bfc7a897247e18@syzkaller.appspotmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/core.c

@@ -221,7 +221,9 @@ static void cfg80211_rfkill_poll(struct rfkill *rfkill, void *data)
 {
 	struct cfg80211_registered_device *rdev = data;
 
+	wiphy_lock(&rdev->wiphy);
 	rdev_rfkill_poll(rdev);
+	wiphy_unlock(&rdev->wiphy);
 }
 
 void cfg80211_stop_p2p_device(struct cfg80211_registered_device *rdev,