ixgbe: fix link test when connected to 1Gbps link partner

This patch is a partial reverse of:
commit dfcc4615
Author: Jacob Keller <jacob.e.keller@intel.com>
Date: Thu Nov 8 07:07:08 2012 +0000

  ixgbe: ethtool ixgbe_diag_test cleanup

Specifically forcing the laser before the link check can lead to
inconsistent results because it does not guarantee that the link will be
negotiated correctly. Such is the case when dual speed SFP+ module is
connected to a gigabit link partner.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>