ixgbe: enable devices with internal switch to read pci parent

This patch modifies the driver to enable certain devices, which have an internal
switch, to read data from the physical slot rather than reading data from the
internal switch. The internal switch will always report the same PCI width and
speed, which is not useful compared to knowing the width and speed of the slot
the physical card is plugged into.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>