ixgbe: propagate XFRM offload state direction instead of flags

Convert the ixgbe driver to rely on XFRM offload state direction instead
of flags bits that were not checked at all.

Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>