Fix description of WR Streamers registers to indicate that latency is always provided in 8ns cycles
This is not stated, but latency (max/min/acc) is always expressed in the stats regs in cycles of 8ns: See pulse_stamper.vhd used in rx_streamer: https://ohwr.org/project/wr-cores/blob/proposed_master/modules/timing/pulse_stamper.vhd#L178
On the other hand for the config of fixed_latency the document says that 16ns is assumed: https://gitlab.cern.ch/BTrain-TEAM/Btrain-over-WhiteRabbit/-/issues/21
and in the end it seems that it depends on the system clock...#96