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

This reverts commit 0dca2c7.

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>

net/sched/cls_flower.c

@@ -1531,13 +1531,14 @@ static int fl_set_key(struct net *net, struct nlattr **tb,
 						       &mask->basic.n_proto,
 						       TCA_FLOWER_UNSPEC,
 						       sizeof(key->basic.n_proto));
-					mask->basic.n_proto = cpu_to_be16(0);
 				} else {
 					key->basic.n_proto = ethertype;
+					mask->basic.n_proto = cpu_to_be16(~0);
 				}
 			}
 		} else {
 			key->basic.n_proto = ethertype;
+			mask->basic.n_proto = cpu_to_be16(~0);
 		}
 	}