mac80211: Allow AP mode to be enabled

With the addition of basic rate set and TX queue parameter
configuration and confirmation that power save buffering is
working again, mac80211 is now in state that allows AP mode to be
used without major problems. Consequently, it is time to allow this
mode to be enabled without having to patch the kernel.

AP mode requires hostapd for management frame processing and as such,
configuring this mode is only allowed through cfg80211 (not with
iwconfig and WEXT).

Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>