igb: reset PHY in the link_up process to recover PHY setting after power down.

There was a previous patch to resolve issue with 82576 losing PHY setting
after PHY power down. However that previous implementation triggered speed
mismatch and occasional link lost. Now, this patch resolves both initial
PHY setting and speed mismatch issues.

Signed-off-by: Akeem G. Abodunrin <akeem.g.abodunrin@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>