net: hns3: add dma_rmb() for rx description

HW can not guarantee complete write desc->rx.size, even though
HNS3_RXD_VLD_B has been set. Driver needs to add dma_rmb()
instruction to make sure desc->rx.size is always valid.

Fixes: e5597095

 ("net: hns3: Add handling of GRO Pkts not fully RX'ed in NAPI poll")
Signed-off-by: Jian Shen <shenjian15@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>