r8169: make ERIAR_EXGMAC the default in eri functions

In basically all eri function calls the type argument is ERIAR_EXGMAC.
Therefore make it the default.

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