Revert "r8169: enable 64-bit DMA by default for PCI Express devices (v2)"

This reverts commit 35317688.

People are reporting problems due to this change and there
is no anticipation that the cause will be tracked down
any time soon.

We can try next time to selectively re-enable this based upon chip
type, or have a black list of some sort.

Signed-off-by: David S. Miller <davem@davemloft.net>