r8169: disable detection of chip version 60

It seems only XID 609 made it to the mass market. Therefore let's
disable detection of the other RTL8125a XID's. If nobody complains
we can remove support for RTL_GIGA_MAC_VER_60 later.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/2cd3df01-5f8b-08dd-6def-3f31a3014bde@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>