[WIRELESS] cfg80211: Update comment for locking.

This patch adds a comment that was part of my rtnl locking patch for
cfg80211 but which I forgot for the merge.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/cfg80211.h

@@ -23,6 +23,10 @@ struct wiphy;
  * All callbacks except where otherwise noted should return 0
  * on success or a negative error code.
  *
+ * All operations are currently invoked under rtnl for consistency with the
+ * wireless extensions but this is subject to reevaluation as soon as this
+ * code is used more widely and we have a first user without wext.
+ *
  * @add_virtual_intf: create a new virtual interface with the given name
  *
  * @del_virtual_intf: remove the virtual interface determined by ifindex.