netdevice ni65: Convert directly reference of netdev->priv

This patch is to kill directly reference of netdev->priv too.
Because the private data needs special memory: lower 16MB DMA.
alloc_etherdev() can not do this work.
So we can't use netdev->priv to point to netdev's private data.
Use netdev->ml_priv instead.

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