r8169: remove default chip versions

Even the chip versions within a family have so many differences that
using a default chip version doesn't really make sense. Instead
of leaving a best case flaky network connectivity, bail out and
report the unknown chip version.

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