cfg80211: add mesh join/leave callback docs

When I made the patch to add mesh join/leave I
didn't pay attention to docs because it was a
proof of concept, and then when we actually did
merge it I forgot -- add docs now.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/cfg80211.h

@@ -1103,6 +1103,8 @@ struct cfg80211_pmksa {
  * @change_mpath: change a given mesh path
  * @get_mpath: get a mesh path for the given parameters
  * @dump_mpath: dump mesh path callback -- resume dump at index @idx
+ * @join_mesh: join the mesh network with the specified parameters
+ * @leave_mesh: leave the current mesh network
  *
  * @get_mesh_config: Get the current mesh configuration
  *