r8169: fix issue with confused RX unit after PHY power-down on RTL8411b

On RTL8411b the RX unit gets confused if the PHY is powered-down.
This was reported in [0] and confirmed by Realtek. Realtek provided
a sequence to fix the RX unit after PHY wakeup.

The issue itself seems to have been there longer, the Fixes tag
refers to where the fix applies properly.

[0] https://bugzilla.redhat.com/show_bug.cgi?id=1692075



Fixes: a99790bf ("r8169: Reinstate ASPM Support")
Tested-by: Ionut Radu <ionut.radu@gmail.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>