This saves some resources (memory in the switching core) as we no longer forward
frames to the endpoints that have no fiber connected.

When high loads of random length traffic was going through the switch, there
were situations that words_total for a new frame was set to
fetch_pg_words(=cur_ll.size) for the previous frame. If fetch_pg_words was a
small number the new frame was reported _done_ soon after it was started in the
OutputBlock. Therefore the rest of the frame was staying in the
async_shrink_fifo making a mess for subsequent frames. The final result was OB
hanging in the frozen_cycle state.

Otherwise, counter gets crazy when watchdog resets the swcore and feeds all the
endpoints and NIC with ack=1.

LVDS was too low for the discrete flip-flop. This was creating spikes on low
half of the signal on some switches.

modules/watchdog: make resetting sequence much longer to be sure we ack everything what is still in the buffers

Conflicts:

	top/scb_18ports/scb_top_synthesis.vhd
	top/scb_8ports/scb_top_synthesis.vhd

Conflicts:

	top/bare_top/scb_top_sim.vhd