net: hns3: use writel() to optimize the barrier operation

writel() can be used to order I/O vs memory by default when
writing portable drivers. Use writel() to replace wmb() +
writel_relaxed(), and writel() is dma_wmb() + writel_relaxed()
for ARM64, so there is an optimization here because dma_wmb()
is a lighter barrier than wmb().

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>