For now it returns a flag that indicated that the device can receive data
from the eth module and flags for the device speed. TODO: Use this callback
in the eth modules before sending data to the device.
- another temporary solution for host from/to little endian conversion
- changed some variable types to bx_bool
- some other small cleanups
- TODO: add boot ROM support to all network devices
- TODO: add save/restore support, use Bochs function for host to little endian
data conversion, timers of networking modules 'vnet' and 'slirp' should use
the device speed instead of fixed 10 MBit
