When we want to support pxelinux-style network booting later, we've got
to do several TFTP transfers - and we do not want to apply for a new IP
address via DHCP each time. So split up net_load into three parts:
1. net_init(), which initializes virtio-net, gets an IP address via DHCP
and prints out the related information.
2. The tftp_load call is now moved directly into the main() function
3. A new net_uninit() function which should tear down the network stack
before we are done in the firmware.
This will make it easier to extend the code in the next patches.
Signed-off-by: Thomas Huth<address@hidden>