[GSoC'20 Update] NetFPGA SUME reference NIC device driver

[Denis Salopek]

Hi everyone!

I implemented the existing Linux driver routines and made the NetFPGA SUME
work as a basic NIC: packet RX/TX currently works and the board forwards
packets from/to the OS (almost certainly with some bugs to fix).
Additionally, I made the driver more "FreeBSD-like", fixed some old but
also newly introduced bugs, and worked on improving code quality and style.
I also started to document and comment on the code.

The TX now works by queuing the packets and sending them only when the FSM
is idle so packets are no longer dropped if the driver is busy.

The next step is improving the RX/TX and adapting the code for integration
with Netmap.

Project github with more details:
https://github.com/denisSal/freebsd-sume

Regards,
Denis Salopek