net/mlx5: Cleanup prototype warning

Cleanup W=1 warning:

drivers/net/ethernet/mellanox/mlx5/core/lag_mp.c:49:
   warning: expecting prototype for Set lag port affinity().
   Prototype was for mlx5_lag_set_port_affinity() instead

Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>