mac80211: Set the correct values for hwmp (1) and airtimeLinkMetric (1)

Per sections 8.4.2.100.2 and 8.4.2.100.3 of Std 802.11-2012

Reported-by: Shinichi Hotori <hotorinn@gmail.com>
Signed-off-by: Javier Cardona <javier@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>