Revert "net-util: add support for Type=ethernet"

This reverts commit 4cd1214db6cf4b262e8ce6381bc710091b375c96.

This may still be fixed in the kernel, revert this for now until
we see how it all shakes out.
udev: net_id - handle virtio buses

This was already supported in path_id, so should be uncontroversial.