wifi: cfg80211: use system_unbound_wq for wiphy work

Since wiphy work items can run pretty much arbitrary
code in the stack/driver, it can take longer to run
all of this, so we shouldn't be using system_wq via
schedule_work(). Also, we lock the wiphy (which is
the reason this exists), so use system_unbound_wq.
Reported-and-tested-by: Kalle Valo <kvalo@kernel.org>
Fixes: a3ee4dc8 ("wifi: cfg80211: add a work abstraction with special semantics")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/core.c

@@ -1622,7 +1622,7 @@ void wiphy_work_queue(struct wiphy *wiphy, struct wiphy_work *work)
 		list_add_tail(&work->entry, &rdev->wiphy_work_list);
 	spin_unlock_irqrestore(&rdev->wiphy_work_lock, flags);
 
-	schedule_work(&rdev->wiphy_work);
+	queue_work(system_unbound_wq, &rdev->wiphy_work);
 }
 EXPORT_SYMBOL_GPL(wiphy_work_queue);