net/mlx5: Give esw_offloads_load/unload_rep() "mlx5_" prefix

As esw_offloads_load/unload_rep() are used outside eswitch.c it is nicer
for them to have "mlx5_" prefix. Add it.

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