net/mlx5: drop unnecessary list_empty

list_for_each_entry is able to handle an empty list.
The only effect of avoiding the loop is not initializing the
index variable.
Drop list_empty tests in cases where these variables are not
used.

Note that list_for_each_entry is defined in terms of list_first_entry,
which indicates that it should not be used on an empty list.  But in
list_for_each_entry, the element obtained by list_first_entry is not
really accessed, only the address of its list_head field is compared
to the address of the list head, so the list_first_entry is safe.

The semantic patch that makes this change is as follows (with another
variant for the no brace case): (http://coccinelle.lip6.fr/)

<smpl>
@@
expression x,e;
iterator name list_for_each_entry;
statement S;
identifier i;
@@

-if (!(list_empty(x))) {
   list_for_each_entry(i,x,...) S
- }
 ... when != i
? i = e
</smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/steering/dr_matcher.c

@@ -474,7 +474,6 @@ static int dr_matcher_add_to_tbl(struct mlx5dr_matcher *matcher)
 	int ret;
 
 	next_matcher = NULL;
-	if (!list_empty(&tbl->matcher_list))
 	list_for_each_entry(tmp_matcher, &tbl->matcher_list, matcher_list) {
 		if (tmp_matcher->prio >= matcher->prio) {
 			next_matcher = tmp_matcher;

drivers/net/ethernet/mellanox/mlx5/core/steering/dr_rule.c

@@ -574,7 +574,6 @@ void mlx5dr_rule_update_rule_member(struct mlx5dr_ste *ste,
 {
 	struct mlx5dr_rule_member *rule_mem;
 
-	if (!list_empty(&ste->rule_list))
 	list_for_each_entry(rule_mem, &ste->rule_list, use_ste_list)
 		rule_mem->ste = new_ste;
 }