fpga: sim: Update struct enum initialization

In Vivado 2021.1, it is no longer allowed to use "default: 0" to
initialize an enum within a packed struct. So we must initalize enum
data members explicitly now.


Original-commit: 8007b6b4dff5b64d476b2e3ccb68a777c2f02c8b

lib/rfnoc/sim/ctrlport_endpoint_tb/ctrlport_endpoint_tb.sv

@@ -305,6 +305,7 @@ module ctrlport_endpoint_tb;
     };
     op_word = '{
       default      : '0,
+      status       : CTRL_STS_OKAY,
       op_code      : ctrl_opcode_t'(opcode),
       byte_enable  : byte_en,
       address      : addr