net/mlx5: E-Switch, Add offloads table

Belongs to the NIC offloads name-space, and to be used as part of the
SRIOV offloads logic to steer packets that hit the e-switch miss rule
to the TIR of the relevant VF representor.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>