net/mlx5: Align sriov/eswitch modules with the new load/unload flow.

Init/cleanup sriov/eswitch in the core software context init/cleanup
flows.
Attach/detach sriov/eswitch in the core load/unload flows.

Signed-off-by: Mohamad Haj Yahia <mohamad@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>