staging-winbond: Kill directly reference of netdev->priv

This driver is not yet finished.
At this time, we don't know how netdev be created and how
private data be allocated.
So, simply use netdev_priv() now and leave some temp comment.

Compile test only.

Signed-off-by: Wang Chen <wangchen@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>