ixgbe: show <2% for encoding loss on PCIe Gen3

This patch updates the ixgbe_check_minimum_link function to correctly show that
there is some minor loss of encoding, even though we don't calculate it in the
max GT/s equation. It is small enough to not bother, but is better to report it
than not.

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>