Use the addrconf_addr_eui48() helper function to set the GUIDs, Also make
sure the GUIDs are valid EUI-64 identifiers.

Link: https://lore.kernel.org/r/20211118100456.45423-1-kamalheib1@gmail.comSigned-off-by: Kamal Heib <kamalheib1@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>