igb: change configure_pcs_link to void since it always returns 0

Since igb_configure_pcs_link always returns 0 there isn't really much point
to checking for the result so it is best just to change this to a void so
we can properly ignore the return result.

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>