r8169: change irq handler to always trigger NAPI polling

This check isn't really needed and we can simplify the code and save
some CPU cycles by removing it. Only in case of an error none of these
bits are set, and calling the NAPI callback doesn't hurt in this case.

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