The cited commit could disable the modify header flag, but did not free
the allocated memory for the modify header actions. Fix it.

Fixes: 27c11b6b ("net/mlx5e: Do not rewrite fields with the same match")
Signed-off-by: Eli Britstein <elibr@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>