r8169: enable SG/TSO on selected chip versions per default

Due to problem reports in the past SG and TSO/TSO6 are disabled per
default. It's not fully clear which chip versions are affected, so we
may impact also users of unaffected chip versions, unless they know
how to use ethtool for enabling SG/TSO/TSO6.
Vendor drivers r8168/r8125 enable SG/TSO/TSO6 for selected chip
versions per default, I'd interpret this as confirmation that these
chip versions are unaffected. So let's do the same here.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>