net/mlx5: Move devlink registration before interfaces load

Register devlink before interfaces are added.
This will allow interfaces to use devlink while initalizing. For example,
call mlx5_is_roce_enabled.

Fixes: aba25279

 ("net/mlx5e: Add TX reporter support")
Signed-off-by: Michael Guralnik <michaelgur@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>