net/mlx5e: Fix freeing flow with kfree() and not kvfree()

Flows are allocated with kzalloc() so free with kfree().

Fixes: 04de7dda ("net/mlx5e: Infrastructure for duplicated offloading of TC flows")
Signed-off-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Eli Britstein <elibr@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>