net/mlx5: E-switch, Return correct error code on group creation failure

Dan Carpenter report:
The patch f47e04eb: "net/mlx5: E-switch, Allow setting share/max
tx rate limits of rate groups" from May 31, 2021, leads to the
following Smatch static checker warning:

	drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c:483 esw_qos_create_rate_group()
	warn: passing zero to 'ERR_PTR'

If min rate normalization failed then error code may be overwritten to 0
if scheduling element destruction succeed. Ignore this value and always
return initial one.

Fixes: f47e04eb ("net/mlx5: E-switch, Allow setting share/max tx rate limits of rate groups")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Dmytro Linkin <dlinkin@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c

@@ -473,10 +473,9 @@ esw_qos_create_rate_group(struct mlx5_eswitch *esw, struct netlink_ext_ack *exta
 
 err_min_rate:
 	list_del(&group->list);
-	err = mlx5_destroy_scheduling_element_cmd(esw->dev,
-						  SCHEDULING_HIERARCHY_E_SWITCH,
-						  group->tsar_ix);
-	if (err)
+	if (mlx5_destroy_scheduling_element_cmd(esw->dev,
+						SCHEDULING_HIERARCHY_E_SWITCH,
+						group->tsar_ix))
 		NL_SET_ERR_MSG_MOD(extack, "E-Switch destroy TSAR for group failed");
 err_sched_elem:
 	kfree(group);