r8169: improve handling task scheduling

r8169: improve handling task scheduling

If we know that the task is going to be a no-op, don't even schedule it.
And remove the check for netif_running() in the worker function, the
check for flag RTL_FLAG_TASK_ENABLED is sufficient. Note that we can't
remove the check for flag RTL_FLAG_TASK_ENABLED in the worker function
because we have no guarantee when it will be executed.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Link: https://lore.kernel.org/r/c65873a3-7394-4107-99a7-83f20030779c@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>