r8169: remove support for chip version RTL_GIGA_MAC_VER_27

This patch is a follow-up to beb401ec

 ("r8169: deprecate support for
RTL_GIGA_MAC_VER_27") that came with 5.12. Nobody complained, so let's
remove support for this chip version.

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