net/core: Add support for configuring VF GUIDs

Add two new NLAs to support configuration of Infiniband node or port
GUIDs. New applications can choose to use this interface to configure
GUIDs with iproute2 with commands such as:

ip link set dev ib0 vf 0 node_guid 00:02:c9:03:00:21:6e:70
ip link set dev ib0 vf 0 port_guid 00:02:c9:03:00:21:6e:78

A new ndo, ndo_sef_vf_guid is introduced to notify the net device of the
request to change the GUID.

Signed-off-by: Eli Cohen <eli@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>