ixgbe: prep IPsec constants for later use

Pull out a couple of values from a function so they can be used
later elsewhere.

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>