Comment 5 for bug 1785859

This is the culprit:

https://git.savannah.gnu.org/cgit/grub.git/commit/grub-core/net?id=9585647a25b65f98db6bd22c569b34795512f046

Removing the parser for bootpath gets rid of the broken additional interface. I expect that checking the return value of grub_ieee1275_get_property() when querying the mac also fixes it, and will investigate that shortly (as it seems the bootpath contains IP addresses, but not MAC addresses).