r8169: improve driver unload and system shutdown behavior on DASH-enabled systems

There's a number of systems supporting DASH remote management.
Driver unload and system shutdown can result in the PHY suspending,
thus making DASH unusable. Improve this by handling DASH being enabled
very similar to WoL being enabled.

Tested-by: Yanko Kaneti <yaneti@declera.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/1de3b176-c09c-1654-6f00-9785f7a4f954@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>