wl12xx: set the AP-started flag only after setting keys

This fix eliminates a potential race between starting the AP role
and setting encryption keys.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>