r8169: fix RTL8168g PHY init

This fixes a copy&paste error in the original patch. Setting the wrong
register resulted in massive packet loss on some systems.

Fixes: a2928d28 ("r8169: use paged versions of phylib MDIO access functions")
Tested-by: Thomas Voegtle <tv@lio96.de>
Signed-off-by: Thomas Voegtle <tv@lio96.de>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>