igb: increase delay for copper link setup

Increase the delay for copper phy init from 15ms to 100ms.  This is to
address issues seen in which ethtool -t was failing in some cases on 82576
based adapters.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>