sch_cake: Fix TC filter flow override and expand it to hosts as well

The TC filter flow mapping override completely skipped the call to
cake_hash(); however that meant that the internal state was not being
updated, which ultimately leads to deadlocks in some configurations. Fix
that by passing the overridden flow ID into cake_hash() instead so it can
react appropriately.

In addition, the major number of the class ID can now be set to override
the host mapping in host isolation mode. If both host and flow are
overridden (or if the respective modes are disabled), flow dissection and
hashing will be skipped entirely; otherwise, the hashing will be kept for
the portions that are not set by the filter.

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>