[Open-graphics] Possible addition to FAQ - bus sniffer

[Dieter]

To help answer the common "why PCI-X rather than PCIe" question,
we might add something like this to the FAQ.

There is a development advantage to PCI.  PCI is a bus, so it is easy
to sniff the bus if things aren't working.  There has been some
discussion about writing software to turn the OGD1 into a PCI bus
sniffer, for developing other boards.