net: typhoon: implement ndo_features_check method

Instead of disabling TSO at compile time if MAX_SKB_FRAGS > 32,
implement ndo_features_check() method for this driver for
a more dynamic handling.

If skb has more than 32 frags and is a GSO packet, force
software segmentation.

Most locally generated packets will use a small number
of fragments anyway.

For forwarding workloads, we can limit gro_max_size at ingress,
we might also implement gro_max_segs if needed.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>