wifi: mac80211: adjust scan cancel comment/check

Instead of the comment about holding RTNL, which is now wrong,
add a proper lockdep assertion for the wiphy mutex.

Fixes: a05829a7 ("cfg80211: avoid holding the RTNL when calling the driver")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230301115906.84352e46f342.Id90fef8c581cebe19cb30274340cf43885d55c74@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/scan.c

@@ -9,7 +9,7 @@
  * Copyright 2007, Michael Wu <flamingice@sourmilk.net>
  * Copyright 2013-2015  Intel Mobile Communications GmbH
  * Copyright 2016-2017  Intel Deutschland GmbH
- * Copyright (C) 2018-2021 Intel Corporation
+ * Copyright (C) 2018-2022 Intel Corporation
  */
 
 #include <linux/if_arp.h>
@@ -1246,11 +1246,11 @@ int ieee80211_request_ibss_scan(struct ieee80211_sub_if_data *sdata,
 	return ret;
 }
 
-/*
- * Only call this function when a scan can't be queued -- under RTNL.
- */
 void ieee80211_scan_cancel(struct ieee80211_local *local)
 {
+	/* ensure a new scan cannot be queued */
+	lockdep_assert_wiphy(local->hw.wiphy);
+
 	/*
 	 * We are canceling software scan, or deferred scan that was not
 	 * yet really started (see __ieee80211_start_scan ).