net/mlx5: Geneve, Fix handling of Geneve object id as error code

On success, mlx5_geneve_tlv_option_create returns non negative
Geneve object id. In case the object id is positive value the
caller functions will handle it as an error (non zero) and
will fail to offload the Geneve rule.

Fix this by changing caller function ,mlx5_geneve_tlv_option_add,
to return 0 in case valid non negative object id was provided.

Fixes: 0ccc171e ("net/mlx5: Geneve, Manage Geneve TLV options")
Signed-off-by: Maor Dickman <maord@nvidia.com>
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>