net/mlx5: Fix missing return value in mlx5_devlink_eswitch_inline_mode_set()

The return value is missing in this code scenario, add the return value
'0' to the return value 'err'.

Eliminate the follow smatch warning:

drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c:3083
mlx5_devlink_eswitch_inline_mode_set() warn: missing error code 'err'.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Fixes: 8e0aa4bc ("net/mlx5: E-switch, Protect eswitch mode changes")
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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

@@ -3083,8 +3083,11 @@ int mlx5_devlink_eswitch_inline_mode_set(struct devlink *devlink, u8 mode,
 
 	switch (MLX5_CAP_ETH(dev, wqe_inline_mode)) {
 	case MLX5_CAP_INLINE_MODE_NOT_REQUIRED:
-		if (mode == DEVLINK_ESWITCH_INLINE_MODE_NONE)
+		if (mode == DEVLINK_ESWITCH_INLINE_MODE_NONE) {
+			err = 0;
 			goto out;
+		}
+
 		fallthrough;
 	case MLX5_CAP_INLINE_MODE_L2:
 		NL_SET_ERR_MSG_MOD(extack, "Inline mode can't be set");