net/mlx5e: Split TC add rule path for nic vs e-switch

Move to have clear separation on the code path to add nic vs e-switch
flows. While here we break the code that deals with adding offloaded
TC tool to few smaller stages, each on helper function.

Besides getting us simpler and readable code, these are pre-steps
for being able to have two HW flows serving one SW TC flow for some
e-switch use cases.

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