The datasheet is wrong for tXFLG on read and write
  => use 80ns instead of 70ns
Also use a single register input for fd_i
  => makes fast register input mode possible for the pins

thx to Weibin for pointing out bug in eb_config

Note: mac_dest member of wr_sockaddr_t struct doesn't do what it says on the box...

Remove dangerous cast of function pointer type.

This supports passing PREFIX= on the command line of make. This allows
to install to custom places without the need to edit the checkout.

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

master.c:
memory model

lm32.c:
tx buffer
ip checksum

- added debug code

fixed wrong stdint.h include
fxied missing bigendian.h include

TODO: Testing & Debugging

next step: create udp/ip network packet header

This is needed, for example, when attaching a slave to a PCIe bridge.

needs proper implementation, this is just a scratchpad of code snippets.