net/mlx5e: Replace call to MPWQE free with dealloc in interface down flow

No need to expose the MPWQE free function to control path.
The dealloc function already exposed, use it.

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Reviewed-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>