kernel-netlink: Add new automatic hw_offload mode

kernel-netlink: Add new automatic hw_offload mode

Until now there were 2 hw_offload modes: no/yes
* hw_offload = no  : Configure the SA without HW offload.
* hw_offload = yes : Configure the SA with HW offload.
                     In this case, if the device does not support
                     offloading, SA creation will fail.

This commit introduces a new mode: hw_offload = auto
----------------------------------------------------
If the device and kernel support HW offload, configure
the SA with HW offload, but do not fail SA creation otherwise.

Signed-off-by: Adi Nissim <adin@mellanox.com>
Reviewed-by: Aviv Heller <avivh@mellanox.com>