net/mlx5: E-Switch, Set vhca id valid flag when creating indir fwd group

When indirect forward group is created, flow is added with vhca id but
without setting vhca id valid flag which violates the PRM.

Fix by setting the missing flag, vhca id valid.

Fixes: 34ca6535 ("net/mlx5: E-Switch, Indirect table infrastructure")
Signed-off-by: Maor Dickman <maord@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>