net: hns3: streaming dma buffer sync between cpu and device

Right now they are empty functions for our SoC since hardware can keep
cache coherent, but it is still good to align with streaming DMA APIs
as device drivers should not make an assumption of SoC.

Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>