net: add a net pointer to struct fqdir

fqdir will soon be dynamically allocated.

We need to reach the struct net pointer from fqdir,
so add it, and replace the various container_of() constructs
by direct access to the new field.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ieee802154/6lowpan/reassembly.c

@@ -453,7 +453,7 @@ static int __net_init lowpan_frags_init_net(struct net *net)
 	ieee802154_lowpan->fqdir.low_thresh = IPV6_FRAG_LOW_THRESH;
 	ieee802154_lowpan->fqdir.timeout = IPV6_FRAG_TIMEOUT;
 
-	res = fqdir_init(&ieee802154_lowpan->fqdir, &lowpan_frags);
+	res = fqdir_init(&ieee802154_lowpan->fqdir, &lowpan_frags, net);
 	if (res < 0)
 		return res;
 	res = lowpan_frags_ns_sysctl_register(net);