mac80211: document ieee80211_tx_info.pad

Fixes htmldocs warning:

Warning(mac80211.h:379): No description found for parameter 'pad[2]'

Signed-off-by: Kalle Valo <kalle.valo@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
1 file changed