wifi: cfg80211: silence a sparse RCU warning

All we're going to do with this pointer is assign it to
another __rcu pointer, but sparse can't see that, so
use rcu_access_pointer() to silence the warning here.

Fixes: c90b93b5b7 ("wifi: cfg80211: update hidden BSSes to avoid WARN_ON")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/scan.c

@@ -1674,7 +1674,9 @@ cfg80211_update_known_bss(struct cfg80211_registered_device *rdev,
 		if (old == rcu_access_pointer(known->pub.ies))
 			rcu_assign_pointer(known->pub.ies, new->pub.beacon_ies);
 
-		cfg80211_update_hidden_bsses(known, new->pub.beacon_ies, old);
+		cfg80211_update_hidden_bsses(known,
+					     rcu_access_pointer(new->pub.beacon_ies),
+					     old);
 
 		if (old)
 			kfree_rcu((struct cfg80211_bss_ies *)old, rcu_head);