net/mlx5e: skip loopback selftest with !CONFIG_INET

When CONFIG_INET is disabled, the new selftest results in a link
error:

drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.o: In function `mlx5e_test_loopback':
en_selftest.c:(.text.mlx5e_test_loopback+0x2ec): undefined reference to `ip_send_check'
en_selftest.c:(.text.mlx5e_test_loopback+0x34c): undefined reference to `udp4_hwcsum'

This hides the specific test in that configuration.

Fixes: 0952da791c97 ("net/mlx5e: Add support for loopback selftest")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -39,7 +39,9 @@ enum {
 	MLX5E_ST_LINK_STATE,
 	MLX5E_ST_LINK_SPEED,
 	MLX5E_ST_HEALTH_INFO,
+#ifdef CONFIG_INET
 	MLX5E_ST_LOOPBACK,
+#endif
 	MLX5E_ST_NUM,
 };
 
@@ -47,7 +49,9 @@ const char mlx5e_self_tests[MLX5E_ST_NUM][ETH_GSTRING_LEN] = {
 	"Link Test",
 	"Speed Test",
 	"Health Test",
+#ifdef CONFIG_INET
 	"Loopback Test",
+#endif
 };
 
 int mlx5e_self_test_num(struct mlx5e_priv *priv)
@@ -93,6 +97,7 @@ static int mlx5e_test_link_speed(struct mlx5e_priv *priv)
 	return 1;
 }
 
+#ifdef CONFIG_INET
 /* loopback test */
 #define MLX5E_TEST_PKT_SIZE (MLX5_MPWRQ_SMALL_PACKET_THRESHOLD - NET_IP_ALIGN)
 static const char mlx5e_test_text[ETH_GSTRING_LEN] = "MLX5E SELF TEST";
@@ -304,12 +309,15 @@ out:
 	kfree(lbtp);
 	return err;
 }
+#endif
 
 static int (*mlx5e_st_func[MLX5E_ST_NUM])(struct mlx5e_priv *) = {
 	mlx5e_test_link_state,
 	mlx5e_test_link_speed,
 	mlx5e_test_health_info,
-	mlx5e_test_loopback
+#ifdef CONFIG_INET
+	mlx5e_test_loopback,
+#endif
 };
 
 void mlx5e_self_test(struct net_device *ndev, struct ethtool_test *etest,