net/mlx5e: Implement mlx5e interface attach/detach callbacks

Needed to support seamless and lightweight PCI/Internal error recovery.
Implement the attach/detach interface callbacks.
In attach callback we only allocate HW resources.
In detach callback we only deallocate HW resources.
All SW/kernel objects initialzing/destroying is kept in add/remove
callbacks.

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>