openvswitch: fix linking without CONFIG_NF_CONNTRACK_LABELS

When CONFIG_CC_OPTIMIZE_FOR_DEBUGGING is enabled, the compiler
fails to optimize out a dead code path, which leads to a link failure:

net/openvswitch/conntrack.o: In function `ovs_ct_set_labels':
conntrack.c:(.text+0x2e60): undefined reference to `nf_connlabels_replace'

In this configuration, we can take a shortcut, and completely
remove the contrack label code. This may also help the regular
optimization.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/openvswitch/conntrack.c

@@ -1203,7 +1203,8 @@ static int ovs_ct_commit(struct net *net, struct sw_flow_key *key,
 					 &info->labels.mask);
 		if (err)
 			return err;
-	} else if (labels_nonzero(&info->labels.mask)) {
+	} else if (IS_ENABLED(CONFIG_NF_CONNTRACK_LABELS) &&
+		   labels_nonzero(&info->labels.mask)) {
 		err = ovs_ct_set_labels(ct, key, &info->labels.value,
 					&info->labels.mask);
 		if (err)