net/mlx5: SF, Rely on hw table for SF devlink port allocation

Supporting SF allocation is currently checked at two places:
(a) SF devlink port allocator and
(b) SF HW table handler.

Both layers are using HCA CAP to identify it using helper routine
mlx5_sf_supported() and mlx5_sf_max_functions().

Instead, rely on the HW table handler to check if SF is supported
or not.

Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Vu Pham <vuhuong@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>