net/mlx5: Flow steering cmd interface should get the fte when deleting

Previously, deleting a flow steering entry only got the index.
Since the FPGA implementation of FTE's deletion might need to dig
inside the FTE itself, we would like to get the FTE's context.
Changing the interface to pass the FTE context.

Signed-off-by: Aviad Yehezkel <aviadye@mellanox.com>
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>