Previously the driver used pcie_get_minimum_link() to warn when the NIC
is in a slot that can't supply as much bandwidth as the NIC could use.

pcie_get_minimum_link() can be misleading because it finds the slowest link
and the narrowest link (which may be different links) without considering
the total bandwidth of each link.  For a path with a 16 GT/s x1 link and a
2.5 GT/s x16 link, it returns 2.5 GT/s x1, which corresponds to 250 MB/s of
bandwidth, not the true available bandwidth of about 1969 MB/s for a
16 GT/s x1 link.

Use pcie_print_link_status() to report PCIe link speed and possible
limitations instead of implementing this in the driver itself.  This finds
the slowest link in the path to the device by computing the total bandwidth
of each link and compares that with the capabilities of the device.

The dmesg change is:

  - %s (%c%d) PCI-E x%d %s found at mem %lx, IRQ %d, node addr %pM
  + %s (%c%d) PCI-E found at mem %lx, IRQ %d, node addr %pM
  + %u.%03u Gb/s available PCIe bandwidth (%s x%d link)
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>