net/mlx5_core: Modify CQ moderation parameters

Introduce mlx5_core_modify_cq_moderation() to be used by the netdev, to
set hardware coalescing.

Signed-off-by: Rana Shahout <ranas@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>