Commit 947976d ("[netdevice] Do not force a poll on net_tx()")
requires network devices to have TX rings that are sufficiently large
to allow a transmitted response to all packets received during a
single poll.

Reported-by: Robin Smidsrød <robin@smidsrod.no>
Tested-by: Robin Smidsrød <robin@smidsrod.no>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

Suggested-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

This patch adds a native iPXE forcedeth driver and removes the legacy
Etherboot forcedeth driver. It supports 40 different chips, compared
to the original 14.

It has been tested on a NIC with an CK804 Ethernet Controller, and the
results of downloading 5 100mb images in a row have been:
12/11/11/11/11 seconds; booting DSL using pxelinux also succeeded. The
driver has also been tested by chaining undionly.kpxe and it worked.

Signed-off-by: Andrei Faur <da3drus@gmail.com>
Tested-by: Andrei Faur <da3drus@gmail.com>
Tested-by: Guo-Fu Tseng <cooldavid@cooldavid.org>
Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>