net/mlx5e: Move local var definition into ifdef block

New local variable "struct flow_block_offload *f" was added to
mlx5e_setup_tc() in recent rtnl lock removal patches. The variable is used
in code that is only compiled when CONFIG_MLX5_ESWITCH is enabled. This
results compilation warning about unused variable when CONFIG_MLX5_ESWITCH
is not set. Move the variable definition into eswitch-specific code block
from the beginning of mlx5e_setup_tc() function.

Fixes: c9f14470 ("net: sched: add API for registering unlocked offload block callbacks")
Reported-by: tanhuazhong <tanhuazhong@huawei.com>
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx5/core/en_main.c

@@ -3497,16 +3497,18 @@ static int mlx5e_setup_tc(struct net_device *dev, enum tc_setup_type type,
 			  void *type_data)
 {
 	struct mlx5e_priv *priv = netdev_priv(dev);
-	struct flow_block_offload *f = type_data;
 
 	switch (type) {
 #ifdef CONFIG_MLX5_ESWITCH
-	case TC_SETUP_BLOCK:
+	case TC_SETUP_BLOCK: {
+		struct flow_block_offload *f = type_data;
+
 		f->unlocked_driver_cb = true;
 		return flow_block_cb_setup_simple(type_data,
 						  &mlx5e_block_cb_list,
 						  mlx5e_setup_tc_block_cb,
 						  priv, priv, true);
+	}
 #endif
 	case TC_SETUP_QDISC_MQPRIO:
 		return mlx5e_setup_tc_mqprio(priv, type_data);