Revert "r8169: remove not needed call to dma_sync_single_for_device"

This reverts commit f072218c.

As reported by Aaro this patch causes network problems on
MIPS Loongson platform. Therefore revert it.

Fixes: f072218c ("r8169: remove not needed call to dma_sync_single_for_device")
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>