net/mlx5: Introduce offloads steering namespace

Add a new namespace (MLX5_FLOW_NAMESPACE_OFFLOADS) to be populated
with flow steering rules that deal with rules that have have to
be executed before the EN NIC steering rules are matched.

The namespace is located after the bypass name-space and before the
kernel name-space. Therefore, it precedes the HW processing done for
rules set for the kernel NIC name-space.

Under SRIOV, it would allow us to match on e-switch missed packet
and forward them to the relevant VF representor TIR.

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