net/mlx5: E-Switch, Get reg_c0 value on CQE

On RX side create a restore table in OFFLOADS namespace.
This table will match on all values for reg_c0 we will use,
and set it to the flow_tag. This flow tag can then be read on the CQE.

As there is no copy action from reg c0 to flow tag, instead we have to
set the flow tag explictily. We add an API so callers can add all the used
reg_c0 values (tags) and for each of those we add a restore rule.

This will be used in a following patch to save the miss chain mapping
tag on reg_c0 and from it restore the tc chain on the skb.

Signed-off-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Oz Shlomo <ozsh@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>