net/mlx4_core: Don't issue PCIe speed/width checks for VFs

Carrying out PCI speed/width checks through pcie_get_minimum_link()
on VFs yield wrong results, so remove them.

Fixes: b912b2f8 ('net/mlx4_core: Warn if device doesn't have enough PCI bandwidth')
Signed-off-by: Eyal Perry <eyalpe@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>