net/core: Populate VF index in struct ifla_vf_guid

In addition to filling the node_guid and port_guid attributes,
there is a need to populate VF index too, otherwise users of netlink
interface will see same VF index for all VFs.

Fixes: 30aad417 ("net/core: Add support for getting VF GUIDs")
Signed-off-by: Danit Goldberg <danitg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>