net/mlx5e: HW LRO changes/fixes

- Change the maximum LRO session size from 16KB to 64KB
- Reduce the LRO session timeout from 512us to 32us in
  order to reduce the TCP latency of non-LRO'ed flows.
- Fix skb_shinfo(skb)->gso_size and set skb_shinfo(skb)->gso_type.
- Fix a bug accessing un-initialized mdev pointer.

Signed-off-by: Achiad Shochat <achiad@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>