ixgbe: add ipsec offload add and remove SA

Add the functions for setting up and removing offloaded SAs (Security
Associations) with the x540 hardware.  We set up the callback structure
but we don't yet set the hardware feature bit to be sure the XFRM service
won't actually try to use us for an offload yet.

The software tables are made up to mimic the hardware tables to make it
easier to track what's in the hardware, and the SA table index is used
for the XFRM offload handle.  However, there is a hashing field in the
Rx SA tracking that will be used to facilitate faster table searches in
the Rx fast path.

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>