RDMA/siw: Make node GUIDs valid EUI-64 identifiers

>From the IBTA: "GUID (Global Unique Identifier): A globally unique EUI-64
compliant identifier." Make sure that siw GUIDs are valid EUI-64 identifiers.

Link: https://lore.kernel.org/r/20190930231707.48259-6-bvanassche@acm.org


Cc: Bernard Metzler <bmt@zurich.ibm.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>