igb: do not force retry count to 1 on 82580 phy

This change resolves an issue seen in some configurations where the link
may drop to 100Mb/s even though the link itself supports 1000Mb/s.  The
issue was root caused to the fact that we were only trying the link once.
Now instead we will try up to 5 attempts on a faulty cable before
downshifting to 100Mb/s.

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>