r8169: enable ASPM on RTL8106E

The Intel SoC was prevented from entering lower idle state because
of RTL8106E's ASPM was not enabled.

So enable ASPM on RTL8106E (chip version 39).
Now the Intel SoC can enter lower idle state, power consumption and
temperature are much lower.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>