Since libvirt now tries to interpret network device models (unless an
unknow model is used) the documentation didn't make a good job
specifying what is supported.
Rewrite the docs to explicitly list the models which we do parse.
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Jonathon Jongsma <jjongsma@redhat.com>