i40e: Populate and check pci bus speed and width

Call i40e_set_pci_config_data from probe, then check that
we are in a 8GT/s x8 PCIe slot and send a warning if we are not.

Change-Id: I62815c574cee50d2787c50bbe956dde7a7a75a11
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>