net: hns3: introduce ring_to_netdev() in enet module

There are a few places that need to access the netdev of a ring
through ring->tqp->handle->kinfo.netdev, and ring->tqp is a struct
which both in enet and hclge modules, it is better to use the
struct that is only used in enet module.

This patch adds the ring_to_netdev() to access the netdev of ring
through ring->tqp_vector->napi.dev.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>