mlx4: Paravirtualize Node Guids for slaves

This is necessary in order to support > 1 VF/PF in a VM for software
that uses the node guid as a discriminator, such as librdmacm.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <roland@purestorage.com>