We can now successfully boot EFI applications from disk, but users
may want to also run them from a PXE setup.
This patch implements rudimentary network support, allowing a payload
to send and receive network packets.
With this patch, I was able to successfully run grub2 with network
access inside of QEMU's -M xlnx-ep108.
Signed-off-by: Alexander Graf <agraf@suse.de>