nl80211: Use nl80211 for mgmt TX/RX in AP mode

nl80211: Use nl80211 for mgmt TX/RX in AP mode

To achieve this, multiple things are needed:
 1) since hostapd needs to handle *all* action frames,
    make the normal registration only when in a non-AP
    mode, to be able to do this use the new socket
 2) store the frequency in each BSS to be able to give
    the right frequency to nl80211's mgmt-tx operation
 3) make TX status processing reject non-matched cookie
    only in non-AP mode

The whole thing depends on having station-poll support
in the kernel. That's currently a good indicator since
the kernel patches are added together.

Signed-hostap: Johannes Berg <johannes.berg@intel.com>