- Made some things optional to reduce logic when
used with the new xport_sv:
(1) Clocking to sys_clk
(2) Preamble insertion
- New options to CUTTHROUGH faster on the TX path.
The new xport_sv already has a gate to accumulate at
its clock crossing.
Original-commit: a68e7101167a4b5bf7b60ed90d963982aae735b8