r8169: disable detection of bogus xid's 308/388

Several years ago these two entries have been added, but it's not clear
why. There's no trace that there has ever been such a chip version, and
not even the r8101 vendor driver knows these id's. So let's disable
detection, and if nobody complains remove them completely later.

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