net/mlx5e: Match recirculated packet miss in slow table using reg_c1

Previous patch in series that implements stack devices RX path implements
indirect table rules that match on tunnel VNI. After such rule is created
all tunnel traffic is recirculated to root table. However, recirculated
packet might not match on any rules installed in the table (for example,
when IP traffic follows ARP traffic). In that case packets appear on
representor of tunnel endpoint VF instead being redirected to the VF
itself.

Extend slow table with additional flow group that matches on reg_c0 (source
port value set by indirect tables implemented by previous patch in series)
and reg_c1 (special 0xFFF mark). When creating offloads fdb tables, install
one rule per VF vport to match on recirculated miss packets and redirect
them to appropriate VF vport. Modify indirect tables code to also rewrite
reg_c1 with special 0xFFF mark.

Implementation reuses reg_c1 tunnel id bits. This is safe to do because
recirculated packets are always matched before decapsulation.

Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: Dmytro Linkin <dlinkin@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>