r8169: remove comment about apparently non-existing chip versions

It's not clear where these entries came from, and as I wrote in the
comment: Not even Realtek's r8101 driver knows these chip id's.
So remove the comment.

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