FPGA: Synchronize X300 RX frontends on time change

The frontend synchronization upon time change was removed, but is
required to synchronize the RX frontend modules when sharing LOs on
TwinRX.  This change restores the behavior.

Signed-off-by: michael-west <michael.west@ettus.com>


Original-commit: c70b479007ab9f578577dfb5c2de6660e877d9a3

top/e320/e320_core.v

@@ -1021,7 +1021,8 @@ module e320_core #(
    .pps                   (pps_radioclk),
    .tb_timestamp          (radio_time),
    .tb_timestamp_last_pps (),
-   .tb_period_ns_q32      ()
+   .tb_period_ns_q32      (),
+   .tb_changed            ()
   );