Revert "net: fec: fix the warning found by dma debug"

This reverts commit 2b995f63.

Панов Андрей reported the following regression:

"Commit 2b995f63 in 4.0.0-rc3 introduces a
nasty bug in transmit, corrupting packets.

To reproduce:

$ dd if=/dev/zero of=zeros bs=1M count=20
$ md5sum -b zeros
8f4e33f3dc3e414ff94e5fb6905cba8c *zeros

This checksum is correct.

Copy file "zeros" to another host with NFS, and it gets corrupted, checksum is
changed.
File should be big, small amounts of transmit isn't affected.

I use an i.MX6 Quad board.

If this commit is reverted, all works fine."

Reported-by: Панов Андрей <rockford@yandex.ru>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>