r8169: don't try to disable interrupts if NAPI is scheduled already

There's no benefit in trying to disable interrupts if NAPI is
scheduled already. This allows us to save a PCI write in this case.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/78c7f2fb-9772-1015-8c1d-632cbdff253f@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>