wireless: fix kernel-doc warning in net/cfg80211.h

Fix kernel-doc warning in net/cfg80211.h:

Warning(include/net/cfg80211.h:1884): No description found for parameter 'registered'
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

include/net/cfg80211.h

@@ -1810,6 +1810,8 @@ struct wiphy_wowlan_support {
  *	by default for perm_addr. In this case, the mask should be set to
  *	all-zeroes. In this case it is assumed that the device can handle
  *	the same number of arbitrary MAC addresses.
+ * @registered: protects ->resume and ->suspend sysfs callbacks against
+ *	unregister hardware
  * @debugfsdir: debugfs directory used for this wiphy, will be renamed
  *	automatically on wiphy renames
  * @dev: (virtual) struct device for this wiphy