net/mlx5: E-Switch, Simplify representor load/unload callback API

In the load() callback for loading representors we don't really need
struct mlx5_eswitch but struct mlx5_core_dev, pass it directly.

In the unload() callback for unloading representors we don't need the
struct mlx5_eswitch argument, remove it.

Signed-off-by: Mark Bloch <markb@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>