net/mlx5e: drop useless LIST_HEAD

Drop LIST_HEAD where the variable it declares is never used.

These became useless in 244cd96a ("net_sched: remove list_head
from tc_action")

The semantic patch that fixes this problem is as follows:
(http://coccinelle.lip6.fr/

)

// <smpl>
@@
identifier x;
@@
- LIST_HEAD(x);
  ... when != x
// </smpl>

Fixes: 244cd96a ("net_sched: remove list_head from tc_action")
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>