mac80211: add missing kernel-doc

Fix mac80211 kernel-doc missing struct field:

Warning(linux-2.6.27-rc1-git2//net/mac80211/sta_info.h:329): No description found for parameter 'tid_seq[IEEE80211_QOS_CTL_TID_MASK + 1]'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>