hostap: don't use flush_scheduled_work()

flush_scheduled_work() is on its way out.  Drop flush_scheduled_work()
from prism2_free_local_data() and replace it with explicit flushing of
work items on the respective free functions.  Work items in ap_data
are flushed from hostap_free_data() and the ones in local_info from
prism2_free_local_data().

Flush is used instead of cancel as some process and free items from
queue.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jes Sorensen <jes@trained-monkey.org>
Cc: netdev@vger.kernel.org