net/mlx5e: fix mlx5e_tc_tun_update_header_ipv6 dummy definition

The alternative implementation of this function in a header file
is declared as a global symbol, and gets added to every .c file
that includes it, which leads to a link error:

arm-linux-gnueabi-ld: drivers/net/ethernet/mellanox/mlx5/core/en_rx.o: in function `mlx5e_tc_tun_update_header_ipv6':
en_rx.c:(.text+0x0): multiple definition of `mlx5e_tc_tun_update_header_ipv6'; drivers/net/ethernet/mellanox/mlx5/core/en_main.o:en_main.c:(.text+0x0): first defined here

Mark it 'static inline' like the other functions here.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun.h

@@ -76,10 +76,12 @@ int mlx5e_tc_tun_update_header_ipv6(struct mlx5e_priv *priv,
 static inline int
 mlx5e_tc_tun_create_header_ipv6(struct mlx5e_priv *priv,
 				struct net_device *mirred_dev,
-				struct mlx5e_encap_entry *e) { return -EOPNOTSUPP; }
-int mlx5e_tc_tun_update_header_ipv6(struct mlx5e_priv *priv,
-				    struct net_device *mirred_dev,
-				    struct mlx5e_encap_entry *e)
+				struct mlx5e_encap_entry *e)
+{ return -EOPNOTSUPP; }
+static inline int
+mlx5e_tc_tun_update_header_ipv6(struct mlx5e_priv *priv,
+				struct net_device *mirred_dev,
+				struct mlx5e_encap_entry *e)
 { return -EOPNOTSUPP; }
 #endif
 int mlx5e_tc_tun_route_lookup(struct mlx5e_priv *priv,