Hardcoded CONFIG_IEEE80211N to be included to clean up implementation.
More or less all new devices support IEEE 802.11n (HT) and there is not
much need for being able to remove that functionality from the build.
Included this unconditionally to get rid of one more build options and
to keep things simpler.
Signed-off-by: Jouni Malinen <j@w1.fi>
