net/mlx5: Refactor mlx5_add_flow_rule

Reduce the set of arguments passed to mlx5_add_flow_rule
by introducing flow_spec structure.

Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>