ixgbe: process the Tx ipsec offload

If the skb has a security association referenced in the skb, then
set up the Tx descriptor with the ipsec offload bits.  While we're
here, we fix an oddly named field in the context descriptor struct.

Signed-off-by: Shannon Nelson <shannon.nelson@oracle.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>