mac80211: Fix missing kernel-doc notation

Fix the following htmldocs warnings:

  Warning(net/mac80211/sta_info.h:322): No description found for parameter 'drv_unblock_wk'
  Warning(net/mac80211/sta_info.h:322): No description found for parameter 'drv_unblock_wk'

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: John W. Linville <linville@tuxdriver.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>