net/devlink: Add E-Switch encapsulation control

This is an e-switch global knob to enable HW support for applying
encapsulation/decapsulation to VF traffic as part of SRIOV e-switch offloading.

The actual encap/decap is carried out (along with the matching and other actions)
per offloaded e-switch rules, e.g as done when offloading the TC tunnel key action.

Signed-off-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>