Revert "r8169: make use of xmit_more and __netdev_sent_queue"

This reverts commit 2e6eedb4.

Sander reported a regression causing a kernel panic[1],
therefore let's revert this commit.

[1] https://marc.info/?t=154965066400001&r=1&w=2



Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>