Fixed forgotten brackets in last commit

src/core/tcp_out.c

@@ -756,7 +756,7 @@ tcp_enqueue_flags(struct tcp_pcb *pcb, u8_t flags)
 #endif /* LWIP_WND_SCALE */
   }
 #if LWIP_TCP_TIMESTAMPS
-  if ((pcb->flags & TF_TIMESTAMP) {
+  if ((pcb->flags & TF_TIMESTAMP)) {
     /* Make sure the timestamp option is only included in data segments if we
        agreed about it with the remote host. */
     optflags |= TF_SEG_OPTS_TS;