net/mlx5: E-Switch, Unload the representors in the correct order

When changing from switchdev to legacy mode, all the representor port
devices (uplink nic and reps) are cleaned up. Part of this cleaning
process is removing the neigh entries and the hash table containing them.
However, a representor neigh entry might be linked to the uplink port
hash table and if the uplink nic is cleaned first the cleaning of the
representor will end up in null deref.
Fix that by unloading the representors in the opposite order of load.

Fixes: cb67b832 ("net/mlx5e: Introduce SRIOV VF representors")
Signed-off-by: Shahar Klein <shahark@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>