Add pcnet driver

[vinc]

Links:

• https://wiki.osdev.org/AMD_PCNET
• https://pdf1.alldatasheet.com/datasheet-pdf/view/89876/AMD/AM79C970.html

[vinc]

To debug the card launch the emulator with:

cargo run --no-default-features --features serial,dvorak,pcnet --release -- \
  -display none -cpu max -serial stdio -rtc base=localtime -hdc disk.img \
  -m 16 -netdev user,id=u1,hostfwd=tcp::2222-:22 -device pcnet,netdev=u1 \
  -object filter-dump,id=f1,netdev=u1,file=/tmp/qemu.pcap

Listen for packets inside the emulator with:

net config debug on
net dump

Send packets inside the host with:

telnet localhost 2222

Listen for packets inside the host with:

tcpdump -r /tmp/qemu.pcap -v

Send packets inside the emulator with:

net config debug on
dhcp