net/mlx5: drop duplicate header delay.h

Drop duplicate header delay.h from mlx5/core/main.c.

Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Acked-by: Matan Barak <matanb@mellanox.com>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>