cfg80211: configuration for WoWLAN over TCP

Intel Wireless devices are able to make a TCP connection
after suspending, sending some data and waking up when
the connection receives wakeup data (or breaks). Add the
WoWLAN configuration and feature advertising API for it.

Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>