dpif: Fix memory leak while dumping dpif flows.

Leak was detected by running test: "ofproto-dpif - balance-tcp bonding"

Fixes: 0e8f5c6 ("dpif-netdev: Modified ovs-appctl dpctl/dump-flows command")
Signed-off-by: Damijan Skvarc <damjan.skvarc@gmail.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

ofproto/ofproto-dpif.c

@@ -6282,6 +6282,9 @@ ofproto_unixctl_dpif_dump_flows(struct unixctl_conn *conn,
     while (dpif_flow_dump_next(flow_dump_thread, &f, 1)) {
         struct flow flow;
 
+        /* No need for extra info. */
+        free(f.attrs.dp_extra_info);
+
         if ((odp_flow_key_to_flow(f.key, f.key_len, &flow, NULL)
              == ODP_FIT_ERROR)
             || (xlate_lookup_ofproto(ofproto->backer, &flow, NULL, NULL)