ath9k: Replace ath9k_opmode with nl80211_iftype

This patch kills ath9k's ath9k_opmode enum by replacing it with nl80211_iftype.

Signed-off-by: Colin McCabe <colin@cozybit.com>
Signed-off-by: Andrey Yurovsky <andrey@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>