igb: open up SCTP checksum offloads to all MACs 82576 and newer

Going forward the plan is to have the MACs support SCTP checksum offloads
so change the check from == to >=.

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>