net/mlx5: Use system_image_guid to determine bonding

With specific NICs, the PFs may have different PCIe ids like
0001:01:00.0/1 and 0002:02:00:00/1.

For PFs with the same system_image_guid, driver should consider
them under the same physical NIC and they are legal to bond together.

If firmware doesn't support system_image_guid, set it to zero and
fallback to use PCIe ids.

Signed-off-by: Rongwei Liu <rongweil@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>