r8169: enable HW csum and TSO

Enable HW csum and TSO per default except on known buggy chip versions.
Realtek confirmed that RTL8168evl has a HW issue with TSO.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>