r8169: fix operation under forced interrupt threading

r8169: fix operation under forced interrupt threading

For several network drivers it was reported that using
__napi_schedule_irqoff() is unsafe with forced threading. One way to
fix this is switching back to __napi_schedule, but then we lose the
benefit of the irqoff version in general. As stated by Eric it doesn't
make sense to make the minimal hard irq handlers in drivers using NAPI
a thread. Therefore ensure that the hard irq handler is never
thread-ified.

Fixes: 671194f09c20 ("r8169: switch to napi_schedule_irqoff")
Link: https://lkml.org/lkml/2020/10/18/19
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/4d3ef84a-c812-5072-918a-22a6f6468310@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>