net/mlx5e: Remove redundant allocation of spec in create indirect fwd group

mlx5_add_flow_rules supports creating rules without any matches by passing NULL
pointer instead of spec, if NULL is passed it will use a static empty spec.
This make allocation of spec in mlx5_create_indir_fwd_group unnecessary.

Remove the redundant allocation.

Signed-off-by: Maor Dickman <maord@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>