QoS: Drop support for hardcoded ACK rules

QoS: Drop support for hardcoded ACK rules

This feature has to go in order to take advantage of CONNMARK which will
drastically decrease CPU load when passing packets.

We no longer will see every packet in the QOS-INC chain in order to
change classification of that packet. It is also party counter-intuitive
to have parts of one connection in one class and the corresponding ACK
packets in another.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>