IB/ipoib: Add ndo operation for getting VFs GUID attributes

Add ndo operation to the network driver that enables configuring
ipoib_get_vf_guid operation. The operation allows to get a VF port
and node GUIDs.

Signed-off-by: Danit Goldberg <danitg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>