This adds a parameter to chdr_xb_ingress_buff and to chdr_stream_output
to make their packet gates optional. They are included by default.
Having the packet gate in chdr_xb_ingress_buff can reduce contention in
the crossbar. Having the packet gate in chdr_stream_output can reduce
the latency for non-data packets (e.g., stream status updates).
Original-commit: 67e0a5a340c14cb0c6ee170fb17be2c09737d723