cfg80211: fix typo

Fix spelling mistake in cfg80211.h: "lenght" -> "length".
The typo is also in the special comment block which
translates to documentation.
Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -5604,7 +5604,7 @@ void cfg80211_ibss_joined(struct net_device *dev, const u8 *bssid,
  * @dev: network device
  * @macaddr: the MAC address of the new candidate
  * @ie: information elements advertised by the peer candidate
- * @ie_len: lenght of the information elements buffer
+ * @ie_len: length of the information elements buffer
  * @gfp: allocation flags
  *
  * This function notifies cfg80211 that the mesh peer candidate has been