net/mlx5: Implement vports admin state backup/restore

Save the user configuration in the vport sturct.
Restore saved old configuration upon vport enable.

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>