net/mlx5: Make mlx5_eswitch_load/unload_vport() static

mlx5_eswitch_load/unload_vport()() functions are not used
outside of eswitch.c. Make them static.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>