Revert "net/sched: cls_flower: Remove match on n_proto"

Revert "net/sched: cls_flower: Remove match on n_proto"

This reverts commit 0dca2c7404a938cb10c85d0515cee40ed5348788.

The commit in question breaks hardware offload of flower filters.

Quoting Vladimir Oltean <olteanv@gmail.com>:

 fl_hw_replace_filter() and fl_reoffload() create a struct
 flow_cls_offload with a rule->match.mask member derived from the mask
 of the software classifier: &f->mask->key - that same mask that is used
 for initializing the flow dissector keys, and the one from which Boris
 removed the basic.n_proto member because it was bothering him.

Reported-by: Vadym Kochan <vadym.kochan@plvision.eu>
Signed-off-by: Boris Sukholitko <boris.sukholitko@broadcom.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>