ixgbe: fix typo error with software defined pins on 82599

Correcting a simple typo with enabling software defined pins.  I don't
believe this was causing any issues but this is how it was meant to be
implemented.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Evan Swanson <evan.swanson@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>